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• ASP.NET MVC 2 Released

  - by Ricardo Peres

  Get it while it’s hot from here. Also read the release notes.

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• Differences Between NHibernate and Entity Framework

  - by Ricardo Peres

  Introduction NHibernate and Entity Framework are two of the most popular O/RM frameworks on the .NET world. Although they share some functionality, there are some aspects on which they are quite different. This post will describe this differences and will hopefully help you get started with the one you know less. Mind you, this is a personal selection of features to compare, it is by no way an exhaustive list. History First, a bit of history. NHibernate is an open-source project that was first ported from Java’s venerable Hibernate framework, one of the first O/RM frameworks, but nowadays it is not tied to it, for example, it has .NET specific features, and has evolved in different ways from those of its Java counterpart. Current version is 3.3, with 3.4 on the horizon. It currently targets .NET 3.5, but can be used as well in .NET 4, it only makes no use of any of its specific functionality. You can find its home page at NHForge. Entity Framework 1 came out with .NET 3.5 and is now on its second major version, despite being version 4. Code First sits on top of it and but came separately and will also continue to be released out of line with major .NET distributions. It is currently on version 4.3.1 and version 5 will be released together with .NET Framework 4.5. All versions will target the current version of .NET, at the time of their release. Its home location is located at MSDN. Architecture In NHibernate, there is a separation between the Unit of Work and the configuration and model instances. You start off by creating a Configuration object, where you specify all global NHibernate settings such as the database and dialect to use, the batch sizes, the mappings, etc, then you build an ISessionFactory from it. The ISessionFactory holds model and metadata that is tied to a particular database and to the settings that came from the Configuration object, and, there will typically be only one instance of each in a process. Finally, you create instances of ISession from the ISessionFactory, which is the NHibernate representation of the Unit of Work and Identity Map. This is a lightweight object, it basically opens and closes a database connection as required and keeps track of the entities associated with it. ISession objects are cheap to create and dispose, because all of the model complexity is stored in the ISessionFactory and Configuration objects. As for Entity Framework, the ObjectContext/DbContext holds the configuration, model and acts as the Unit of Work, holding references to all of the known entity instances. This class is therefore not lightweight as its NHibernate counterpart and it is not uncommon to see examples where an instance is cached on a field. Mappings Both NHibernate and Entity Framework (Code First) support the use of POCOs to represent entities, no base classes are required (or even possible, in the case of NHibernate). As for mapping to and from the database, NHibernate supports three types of mappings: XML-based, which have the advantage of not tying the entity classes to a particular O/RM; the XML files can be deployed as files on the file system or as embedded resources in an assembly; Attribute-based, for keeping both the entities and database details on the same place at the expense of polluting the entity classes with NHibernate-specific attributes; Strongly-typed code-based, which allows dynamic creation of the model and strongly typing it, so that if, for example, a property name changes, the mapping will also be updated. Entity Framework can use: Attribute-based (although attributes cannot express all of the available possibilities – for example, cascading); Strongly-typed code mappings. Database Support With NHibernate you can use mostly any database you want, including: SQL Server; SQL Server Compact; SQL Server Azure; Oracle; DB2; PostgreSQL; MySQL; Sybase Adaptive Server/SQL Anywhere; Firebird; SQLLite; Informix; Any through OLE DB; Any through ODBC. Out of the box, Entity Framework only supports SQL Server, but a number of providers exist, both free and commercial, for some of the most used databases, such as Oracle and MySQL. See a list here. Inheritance Strategies Both NHibernate and Entity Framework support the three canonical inheritance strategies: Table Per Type Hierarchy (Single Table Inheritance), Table Per Type (Class Table Inheritance) and Table Per Concrete Type (Concrete Table Inheritance). Associations Regarding associations, both support one to one, one to many and many to many. However, NHibernate offers far more collection types: Bags of entities or values: unordered, possibly with duplicates; Lists of entities or values: ordered, indexed by a number column; Maps of entities or values: indexed by either an entity or any value; Sets of entities or values: unordered, no duplicates; Arrays of entities or values: indexed, immutable. Querying NHibernate exposes several querying APIs: LINQ is probably the most used nowadays, and really does not need to be introduced; Hibernate Query Language (HQL) is a database-agnostic, object-oriented SQL-alike language that exists since NHibernate’s creation and still offers the most advanced querying possibilities; well suited for dynamic queries, even if using string concatenation; Criteria API is an implementation of the Query Object pattern where you create a semi-abstract conceptual representation of the query you wish to execute by means of a class model; also a good choice for dynamic querying; Query Over offers a similar API to Criteria, but using strongly-typed LINQ expressions instead of strings; for this, although more refactor-friendlier that Criteria, it is also less suited for dynamic queries; SQL, including stored procedures, can also be used; Integration with Lucene.NET indexer is available. As for Entity Framework: LINQ to Entities is fully supported, and its implementation is considered very complete; it is the API of choice for most developers; Entity-SQL, HQL’s counterpart, is also an object-oriented, database-independent querying language that can be used for dynamic queries; SQL, of course, is also supported. Caching Both NHibernate and Entity Framework, of course, feature first-level cache. NHibernate also supports a second-level cache, that can be used among multiple ISessionFactorys, even in different processes/machines: Hashtable (in-memory); SysCache (uses ASP.NET as the cache provider); SysCache2 (same as above but with support for SQL Server SQL Dependencies); Prevalence; SharedCache; Memcached; Redis; NCache; Appfabric Caching. Out of the box, Entity Framework does not have any second-level cache mechanism, however, there are some public samples that show how we can add this. ID Generators NHibernate supports different ID generation strategies, coming from the database and otherwise: Identity (for SQL Server, MySQL, and databases who support identity columns); Sequence (for Oracle, PostgreSQL, and others who support sequences); Trigger-based; HiLo; Sequence HiLo (for databases that support sequences); Several GUID flavors, both in GUID as well as in string format; Increment (for single-user uses); Assigned (must know what you’re doing); Sequence-style (either uses an actual sequence or a single-column table); Table of ids; Pooled (similar to HiLo but stores high values in a table); Native (uses whatever mechanism the current database supports, identity or sequence). Entity Framework only supports: Identity generation; GUIDs; Assigned values. Properties NHibernate supports properties of entity types (one to one or many to one), collections (one to many or many to many) as well as scalars and enumerations. It offers a mechanism for having complex property types generated from the database, which even include support for querying. It also supports properties originated from SQL formulas. Entity Framework only supports scalars, entity types and collections. Enumerations support will come in the next version. Events and Interception NHibernate has a very rich event model, that exposes more than 20 events, either for synchronous pre-execution or asynchronous post-execution, including: Pre/Post-Load; Pre/Post-Delete; Pre/Post-Insert; Pre/Post-Update; Pre/Post-Flush. It also features interception of class instancing and SQL generation. As for Entity Framework, only two events exist: ObjectMaterialized (after loading an entity from the database); SavingChanges (before saving changes, which include deleting, inserting and updating). Tracking Changes For NHibernate as well as Entity Framework, all changes are tracked by their respective Unit of Work implementation. Entities can be attached and detached to it, Entity Framework does, however, also support self-tracking entities. Optimistic Concurrency Control NHibernate supports all of the imaginable scenarios: SQL Server’s ROWVERSION; Oracle’s ORA_ROWSCN; A column containing date and time; A column containing a version number; All/dirty columns comparison. Entity Framework is more focused on Entity Framework, so it only supports: SQL Server’s ROWVERSION; Comparing all/some columns. Batching NHibernate has full support for insertion batching, but only if the ID generator in use is not database-based (for example, it cannot be used with Identity), whereas Entity Framework has no batching at all. Cascading Both support cascading for collections and associations: when an entity is deleted, their conceptual children are also deleted. NHibernate also offers the possibility to set the foreign key column on children to NULL instead of removing them. Flushing Changes NHibernate’s ISession has a FlushMode property that can have the following values: Auto: changes are sent to the database when necessary, for example, if there are dirty instances of an entity type, and a query is performed against this entity type, or if the ISession is being disposed; Commit: changes are sent when committing the current transaction; Never: changes are only sent when explicitly calling Flush(). As for Entity Framework, changes have to be explicitly sent through a call to AcceptAllChanges()/SaveChanges(). Lazy Loading NHibernate supports lazy loading for Associated entities (one to one, many to one); Collections (one to many, many to many); Scalar properties (thing of BLOBs or CLOBs). Entity Framework only supports lazy loading for: Associated entities; Collections. Generating and Updating the Database Both NHibernate and Entity Framework Code First (with the Migrations API) allow creating the database model from the mapping and updating it if the mapping changes. Extensibility As you can guess, NHibernate is far more extensible than Entity Framework. Basically, everything can be extended, from ID generation, to LINQ to SQL transformation, HQL native SQL support, custom column types, custom association collections, SQL generation, supported databases, etc. With Entity Framework your options are more limited, at least, because practically no information exists as to what can be extended/changed. It features a provider model that can be extended to support any database. Integration With Other Microsoft APIs and Tools When it comes to integration with Microsoft technologies, it will come as no surprise that Entity Framework offers the best support. For example, the following technologies are fully supported: ASP.NET (through the EntityDataSource); ASP.NET Dynamic Data; WCF Data Services; WCF RIA Services; Visual Studio (through the integrated designer). Documentation This is another point where Entity Framework is superior: NHibernate lacks, for starters, an up to date API reference synchronized with its current version. It does have a community mailing list, blogs and wikis, although not much used. Entity Framework has a number of resources on MSDN and, of course, several forums and discussion groups exist. Conclusion Like I said, this is a personal list. I may come as a surprise to some that Entity Framework is so behind NHibernate in so many aspects, but it is true that NHibernate is much older and, due to its open-source nature, is not tied to product-specific timeframes and can thus evolve much more rapidly. I do like both, and I chose whichever is best for the job I have at hands. I am looking forward to the changes in EF5 which will add significant value to an already interesting product. So, what do you think? Did I forget anything important or is there anything else worth talking about? Looking forward for your comments!

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• Oracle Coherence, Split-Brain and Recovery Protocols In Detail

  - by Ricardo Ferreira

  This article provides a high level conceptual overview of Split-Brain scenarios in distributed systems. It will focus on a specific example of cluster communication failure and recovery in Oracle Coherence. This includes a discussion on the witness protocol (used to remove failed cluster members) and the panic protocol (used to resolve Split-Brain scenarios). Note that the removal of cluster members does not necessarily indicate a Split-Brain condition. Oracle Coherence does not (and cannot) detect a Split-Brain as it occurs, the condition is only detected when cluster members that previously lost contact with each other regain contact. Cluster Topology and Configuration In order to create an good didactic for the article, let's assume a cluster topology and configuration. In this example we have a six member cluster, consisting of one JVM on each physical machine. The member IDs are as follows: Member ID  IP Address  1  10.149.155.76  2  10.149.155.77  3  10.149.155.236  4  10.149.155.75  5  10.149.155.79  6  10.149.155.78 Members 1, 2, and 3 are connected to a switch, and members 4, 5, and 6 are connected to a second switch. There is a link between the two switches, which provides network connectivity between all of the machines. Member 1 is the first member to join this cluster, thus making it the senior member. Member 6 is the last member to join this cluster. Here is a log snippet from Member 6 showing the complete member set: 2010-02-26 15:27:57.390/3.062 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=main, member=6): Started DefaultCacheServer... SafeCluster: Name=cluster:0xDDEB Group{Address=224.3.5.3, Port=35465, TTL=4} MasterMemberSet ( ThisMember=Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) OldestMember=Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) ActualMemberSet=MemberSet(Size=6, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) Member(Id=2, Timestamp=2010-02-26 15:27:17.847, Address=10.149.155.77:8088, MachineId=1101, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:296, Role=CoherenceServer) Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer) Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) Member(Id=5, Timestamp=2010-02-26 15:27:49.095, Address=10.149.155.79:8088, MachineId=1103, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:3229, Role=CoherenceServer) Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) ) RecycleMillis=120000 RecycleSet=MemberSet(Size=0, BitSetCount=0 ) ) At approximately 15:30, the connection between the two switches is severed: Thirty seconds later (the default packet timeout in development mode) the logs indicate communication failures across the cluster. In this example, the communication failure was caused by a network failure. In a production setting, this type of communication failure can have many root causes, including (but not limited to) network failures, excessive GC, high CPU utilization, swapping/virtual memory, and exceeding maximum network bandwidth. In addition, this type of failure is not necessarily indicative of a split brain. Any communication failure will be logged in this fashion. Member 2 logs a communication failure with Member 5: 2010-02-26 15:30:32.638/196.928 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=PacketPublisher, member=2): Timeout while delivering a packet; requesting the departure confirmation for Member(Id=5, Timestamp=2010-02-26 15:27:49.095, Address=10.149.155.79:8088, MachineId=1103, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:3229, Role=CoherenceServer) by MemberSet(Size=2, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) ) The Coherence clustering protocol (TCMP) is a reliable transport mechanism built on UDP. In order for the protocol to be reliable, it requires an acknowledgement (ACK) for each packet delivered. If a packet fails to be acknowledged within the configured timeout period, the Coherence cluster member will log a packet timeout (as seen in the log message above). When this occurs, the cluster member will consult with other members to determine who is at fault for the communication failure. If the witness members agree that the suspect member is at fault, the suspect is removed from the cluster. If the witnesses unanimously disagree, the accuser is removed. This process is known as the witness protocol. Since Member 2 cannot communicate with Member 5, it selects two witnesses (Members 1 and 4) to determine if the communication issue is with Member 5 or with itself (Member 2). However, Member 4 is on the switch that is no longer accessible by Members 1, 2 and 3; thus a packet timeout for member 4 is recorded as well: 2010-02-26 15:30:35.648/199.938 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=PacketPublisher, member=2): Timeout while delivering a packet; requesting the departure confirmation for Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) by MemberSet(Size=2, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) ) Member 1 has the ability to confirm the departure of member 4, however Member 6 cannot as it is also inaccessible. At the same time, Member 3 sends a request to remove Member 6, which is followed by a report from Member 3 indicating that Member 6 has departed the cluster: 2010-02-26 15:30:35.706/199.996 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=2): MemberLeft request for Member 6 received from Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer) 2010-02-26 15:30:35.709/199.999 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=2): MemberLeft notification for Member 6 received from Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer) The log for Member 3 determines how Member 6 departed the cluster: 2010-02-26 15:30:35.161/191.694 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=PacketPublisher, member=3): Timeout while delivering a packet; requesting the departure confirmation for Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) by MemberSet(Size=2, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) Member(Id=2, Timestamp=2010-02-26 15:27:17.847, Address=10.149.155.77:8088, MachineId=1101, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:296, Role=CoherenceServer) ) 2010-02-26 15:30:35.165/191.698 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=Cluster, member=3): Member departure confirmed by MemberSet(Size=2, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) Member(Id=2, Timestamp=2010-02-26 15:27:17.847, Address=10.149.155.77:8088, MachineId=1101, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:296, Role=CoherenceServer) ); removing Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) In this case, Member 3 happened to select two witnesses that it still had connectivity with (Members 1 and 2) thus resulting in a simple decision to remove Member 6. Given the departure of Member 6, Member 2 is left with a single witness to confirm the departure of Member 4: 2010-02-26 15:30:35.713/200.003 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=Cluster, member=2): Member departure confirmed by MemberSet(Size=1, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) ); removing Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) In the meantime, Member 4 logs a missing heartbeat from the senior member. This message is also logged on Members 5 and 6. 2010-02-26 15:30:07.906/150.453 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=PacketListenerN, member=4): Scheduled senior member heartbeat is overdue; rejoining multicast group. Next, Member 4 logs a TcpRing failure with Member 2, thus resulting in the termination of Member 2: 2010-02-26 15:30:21.421/163.968 Oracle Coherence GE 3.5.3/465p2 <D4> (thread=Cluster, member=4): TcpRing: Number of socket exceptions exceeded maximum; last was "java.net.SocketTimeoutException: connect timed out"; removing the member: 2 For quick process termination detection, Oracle Coherence utilizes a feature called TcpRing which is a sparse collection of TCP/IP-based connections between different members in the cluster. Each member in the cluster is connected to at least one other member, which (if at all possible) is running on a different physical box. This connection is not used for any data transfer, only heartbeat communications are sent once a second per each link. If a certain number of exceptions are thrown while trying to re-establish a connection, the member throwing the exceptions is removed from the cluster. Member 5 logs a packet timeout with Member 3 and cites witnesses Members 4 and 6: 2010-02-26 15:30:29.791/165.037 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=PacketPublisher, member=5): Timeout while delivering a packet; requesting the departure confirmation for Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer) by MemberSet(Size=2, BitSetCount=2 Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) ) 2010-02-26 15:30:29.798/165.044 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=Cluster, member=5): Member departure confirmed by MemberSet(Size=2, BitSetCount=2 Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) ); removing Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer) Eventually we are left with two distinct clusters consisting of Members 1, 2, 3 and Members 4, 5, 6, respectively. In the latter cluster, Member 4 is promoted to senior member. The connection between the two switches is restored at 15:33. Upon the restoration of the connection, the cluster members immediately receive cluster heartbeats from the two senior members. In the case of Members 1, 2, and 3, the following is logged: 2010-02-26 15:33:14.970/369.066 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=Cluster, member=1): The member formerly known as Member(Id=4, Timestamp=2010-02-26 15:30:35.341, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) has been forcefully evicted from the cluster, but continues to emit a cluster heartbeat; henceforth, the member will be shunned and its messages will be ignored. Likewise for Members 4, 5, and 6: 2010-02-26 15:33:14.343/336.890 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=Cluster, member=4): The member formerly known as Member(Id=1, Timestamp=2010-02-26 15:30:31.64, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) has been forcefully evicted from the cluster, but continues to emit a cluster heartbeat; henceforth, the member will be shunned and its messages will be ignored. This message indicates that a senior heartbeat is being received from members that were previously removed from the cluster, in other words, something that should not be possible. For this reason, the recipients of these messages will initially ignore them. After several iterations of these messages, the existence of multiple clusters is acknowledged, thus triggering the panic protocol to reconcile this situation. When the presence of more than one cluster (i.e. Split-Brain) is detected by a Coherence member, the panic protocol is invoked in order to resolve the conflicting clusters and consolidate into a single cluster. The protocol consists of the removal of smaller clusters until there is one cluster remaining. In the case of equal size clusters, the one with the older Senior Member will survive. Member 1, being the oldest member, initiates the protocol: 2010-02-26 15:33:45.970/400.066 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=Cluster, member=1): An existence of a cluster island with senior Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) containing 3 nodes have been detected. Since this Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) is the senior of an older cluster island, the panic protocol is being activated to stop the other island's senior and all junior nodes that belong to it. Member 3 receives the panic: 2010-02-26 15:33:45.803/382.336 Oracle Coherence GE 3.5.3/465p2 <Error> (thread=Cluster, member=3): Received panic from senior Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) caused by Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) Member 4, the senior member of the younger cluster, receives the kill message from Member 3: 2010-02-26 15:33:44.921/367.468 Oracle Coherence GE 3.5.3/465p2 <Error> (thread=Cluster, member=4): Received a Kill message from a valid Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer); stopping cluster service. In turn, Member 4 requests the departure of its junior members 5 and 6: 2010-02-26 15:33:44.921/367.468 Oracle Coherence GE 3.5.3/465p2 <Error> (thread=Cluster, member=4): Received a Kill message from a valid Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer); stopping cluster service. 2010-02-26 15:33:43.343/349.015 Oracle Coherence GE 3.5.3/465p2 <Error> (thread=Cluster, member=6): Received a Kill message from a valid Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer); stopping cluster service. Once Members 4, 5, and 6 restart, they rejoin the original cluster with senior member 1. The log below is from Member 4. Note that it receives a different member id when it rejoins the cluster. 2010-02-26 15:33:44.921/367.468 Oracle Coherence GE 3.5.3/465p2 <Error> (thread=Cluster, member=4): Received a Kill message from a valid Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer); stopping cluster service. 2010-02-26 15:33:46.921/369.468 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Service Cluster left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Invocation:InvocationService, member=4): Service InvocationService left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=OptimisticCache, member=4): Service OptimisticCache left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=ReplicatedCache, member=4): Service ReplicatedCache left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=DistributedCache, member=4): Service DistributedCache left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Invocation:Management, member=4): Service Management left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member 6 left service Management with senior member 5 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member 6 left service DistributedCache with senior member 5 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member 6 left service ReplicatedCache with senior member 5 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member 6 left service OptimisticCache with senior member 5 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member 6 left service InvocationService with senior member 5 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member(Id=6, Timestamp=2010-02-26 15:33:47.046, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) left Cluster with senior member 4 2010-02-26 15:33:49.218/371.765 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=main, member=n/a): Restarting cluster 2010-02-26 15:33:49.421/371.968 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=n/a): Service Cluster joined the cluster with senior service member n/a 2010-02-26 15:33:49.625/372.172 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=Cluster, member=n/a): This Member(Id=5, Timestamp=2010-02-26 15:33:50.499, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer, Edition=Grid Edition, Mode=Development, CpuCount=2, SocketCount=1) joined cluster "cluster:0xDDEB" with senior Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer, Edition=Grid Edition, Mode=Development, CpuCount=2, SocketCount=2) Cool isn't it?

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• Sending Messages to SignalR Hubs from the Outside

  - by Ricardo Peres

  Introduction You are by now probably familiarized with SignalR, Microsoft’s API for real-time web functionality. This is, in my opinion, one of the greatest products Microsoft has released in recent time. Usually, people login to a site and enter some page which is connected to a SignalR hub. Then they can send and receive messages – not just text messages, mind you – to other users in the same hub. Also, the server can also take the initiative to send messages to all or a specified subset of users on its own, this is known as server push. The normal flow is pretty straightforward, Microsoft has done a great job with the API, it’s clean and quite simple to use. And for the latter – the server taking the initiative – it’s also quite simple, just involves a little more work. The Problem The API for sending messages can be achieved from inside a hub – an instance of the Hub class – which is something that we don’t have if we are the server and we want to send a message to some user or group of users: the Hub instance is only instantiated in response to a client message. The Solution It is possible to acquire a hub’s context from outside of an actual Hub instance, by calling GlobalHost.ConnectionManager.GetHubContext<T>(). This API allows us to: Broadcast messages to all connected clients (possibly excluding some); Send messages to a specific client; Send messages to a group of clients. So, we have groups and clients, each is identified by a string. Client strings are called connection ids and group names are free-form, given by us. The problem with client strings is, we do not know how these map to actual users. One way to achieve this mapping is by overriding the Hub’s OnConnected and OnDisconnected methods and managing the association there. Here’s an example: 1: public class MyHub : Hub 2: { 3: private static readonly IDictionary<String, ISet<String>> users = new ConcurrentDictionary<String, ISet<String>>(); 4:  5: public static IEnumerable<String> GetUserConnections(String username) 6: { 7: ISet<String> connections; 8:  9: users.TryGetValue(username, out connections); 10:  11: return (connections ?? Enumerable.Empty<String>()); 12: } 13:  14: private static void AddUser(String username, String connectionId) 15: { 16: ISet<String> connections; 17:  18: if (users.TryGetValue(username, out connections) == false) 19: { 20: connections = users[username] = new HashSet<String>(); 21: } 22:  23: connections.Add(connectionId); 24: } 25:  26: private static void RemoveUser(String username, String connectionId) 27: { 28: users[username].Remove(connectionId); 29: } 30:  31: public override Task OnConnected() 32: { 33: AddUser(this.Context.Request.User.Identity.Name, this.Context.ConnectionId); 34: return (base.OnConnected()); 35: } 36:  37: public override Task OnDisconnected() 38: { 39: RemoveUser(this.Context.Request.User.Identity.Name, this.Context.ConnectionId); 40: return (base.OnDisconnected()); 41: } 42: } As you can see, I am using a static field to store the mapping between a user and its possibly many connections – for example, multiple open browser tabs or even multiple browsers accessing the same page with the same login credentials. The user identity, as is normal in .NET, is obtained from the IPrincipal which in SignalR hubs case is stored in Context.Request.User. Of course, this property will only have a meaningful value if we enforce authentication. Another way to go is by creating a group for each user that connects: 1: public class MyHub : Hub 2: { 3: public override Task OnConnected() 4: { 5: this.Groups.Add(this.Context.ConnectionId, this.Context.Request.User.Identity.Name); 6: return (base.OnConnected()); 7: } 8:  9: public override Task OnDisconnected() 10: { 11: this.Groups.Remove(this.Context.ConnectionId, this.Context.Request.User.Identity.Name); 12: return (base.OnDisconnected()); 13: } 14: } In this case, we will have a one-to-one equivalence between users and groups. All connections belonging to the same user will fall in the same group. So, if we want to send messages to a user from outside an instance of the Hub class, we can do something like this, for the first option – user mappings stored in a static field: 1: public void SendUserMessage(String username, String message) 2: { 3: var context = GlobalHost.ConnectionManager.GetHubContext<MyHub>(); 4: 5: foreach (String connectionId in HelloHub.GetUserConnections(username)) 6: { 7: context.Clients.Client(connectionId).sendUserMessage(message); 8: } 9: } And for using groups, its even simpler: 1: public void SendUserMessage(String username, String message) 2: { 3: var context = GlobalHost.ConnectionManager.GetHubContext<MyHub>(); 4:  5: context.Clients.Group(username).sendUserMessage(message); 6: } Using groups has the advantage that the IHubContext interface returned from GetHubContext has direct support for groups, no need to send messages to individual connections. Of course, you can wrap both mapping options in a common API, perhaps exposed through IoC. One example of its interface might be: 1: public interface IUserToConnectionMappingService 2: { 3: //associate and dissociate connections to users 4:  5: void AddUserConnection(String username, String connectionId); 6:  7: void RemoveUserConnection(String username, String connectionId); 8: } SignalR has built-in dependency resolution, by means of the static GlobalHost.DependencyResolver property: 1: //for using groups (in the Global class) 2: GlobalHost.DependencyResolver.Register(typeof(IUserToConnectionMappingService), () => new GroupsMappingService()); 3:  4: //for using a static field (in the Global class) 5: GlobalHost.DependencyResolver.Register(typeof(IUserToConnectionMappingService), () => new StaticMappingService()); 6:  7: //retrieving the current service (in the Hub class) 8: var mapping = GlobalHost.DependencyResolver.Resolve<IUserToConnectionMappingService>(); Now all you have to do is implement GroupsMappingService and StaticMappingService with the code I shown here and change SendUserMessage method to rely in the dependency resolver for the actual implementation. Stay tuned for more SignalR posts!

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• NHibernate 2 Beginner's Guide Review

  - by Ricardo Peres

  OK, here's the review I promised a while ago. This is a beginner's introduction to NHibernate, so if you have already some experience with NHibernate, you will notice it lacks a lot of concepts and information. It starts with a good description of NHibernate and why would we use it. It goes on describing basic mapping scenarios having primary keys generated with the HiLo or Identity algorithms, without actually explaining why would we choose one over the other. As for mapping, the book talks about XML mappings and provides a simple example of Fluent NHibernate, comparing it to its XML counterpart. When it comes to relations, it covers one-to-many/many-to-one and many-to-many, not one-to-one relations, but only talks briefly about lazy loading, which is, IMO, an important concept. Only Bags are described, not any of the other collection types. The log4net configuration description gets it's own chapter, which I find excessive. The chapter on configuration merely lists the most common properties for configuring NHibernate, both in XML and in code. Querying only talks about loading by ID (using Get, not Load) and using Criteria API, on which a paging example is presented as well as some common filtering options (property equals/like/between to, no examples on conjunction/disjunction, however). There's a chapter fully dedicated to ASP.NET, which explains how we can use NHibernate in web applications. It basically talks about ASP.NET concepts, though. Following it, another chapter explains how we can build our own ASP.NET providers using NHibernate (Membership, Role). The available entity generators for NHibernate are referred and evaluated on a chapter of their own, the list is fine (CodeSmith, nhib-gen, AjGenesis, Visual NHibernate, MyGeneration, NGen, NHModeler, Microsoft T4 (?) and hbm2net), examples are provided whenever possible, however, I have some problems with some of the evaluations: for example, Visual NHibernate scores 5 out of 5 on Visual Studio integration, which simply does not exist! I suspect the author means to say that it can be launched from inside Visual Studio, but then, what can't? Finally, there's a chapter I really don't understand. It seems like a bag where a lot of things are thrown in, like NHibernate Burrow (which actually isn't explained at all), Blog.Net components, CSS template conversion and web.config settings related to the maximum request length for file uploads and ending with XML configuration, with the help of GhostDoc. Like I said, the book is only good for absolute beginners, it does a fair job in explaining the very basics, but lack a lot of not-so-basic concepts. Among other things, it lacks: Inheritance mapping strategies (table per class hierarchy, table per class, table per concrete class) Load versus Get usage Other usefull ISession methods First level cache (Identity Map pattern) Other collection types other that Bag (Set, List, Map, IdBag, etc Fetch options User Types Filters Named queries LINQ examples HQL examples And that's it! I hope you find this review useful. The link to the book site is https://www.packtpub.com/nhibernate-2-x-beginners-guide/book

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• Exam 71-515: TS: Web Applications Development with Microsoft .NET Framework 4

  - by Ricardo Peres

  I took the 71-515 exam today. 85 questions, 240 minutes. Here are some notes: Great number of jQuery questions, mostly having to do with AJAX Lots of MVC 2 questions also A number of classic ASP.NET web forms, of which only a few were related with the new 4 features Some Entity Framework Some plain old JavaScript, like, changing an image dynamically I think I did OK. As with my previous exam, I still don't know if I passed or not, will have to wait for the end of the beta period.

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• Windows Presentation Foundation 4.5 Cookbook Review

  - by Ricardo Peres

  As promised, here’s my review of Windows Presentation Foundation 4.5 Cookbook, that Packt Publishing kindly made available to me. It is an introductory book, targeted at WPF newcomers or users with few experience, following the typical recipes or cookbook style. Like all Packt Publishing books on development, each recipe comes with sample code that is self-sufficient for understanding the concepts it tries to illustrate. It starts on chapter 1 by introducing the most important concepts, the XAML language itself, what can be declared in XAML and how to do it, what are dependency and attached properties as well as markup extensions and events, which should give readers a most required introduction to how WPF works and how to do basic stuff. It moves on to resources on chapter 2, which also makes since, since it’s such an important concept in WPF. Next, chapter 3, come the panels used for laying controls on the screen, all of the out of the box panels are described with typical use cases. Controls come next in chapter 4; the difference between elements and controls is introduced, as well as content controls, headered controls and items controls, and all standard controls are introduced. The book shows how to change the way they look by using templates. The next chapter, 5, talks about top level windows and the WPF application object: how to access startup arguments, how to set the main window, using standard dialogs and there’s even a sample on how to have a irregularly-shaped window. This is one of the most important concepts in WPF: data binding, which is the theme for the following chapter, 6. All common scenarios are introduced, the binding modes, directions, triggers, etc. It talks about the INotifyPropertyChanged interface and how to use it for notifying data binding subscribers of changes in data sources. Data templates and selectors are also covered, as are value converters and data triggers. Examples include master-detail and sorting, grouping and filtering collections and binding trees and grids. Last it covers validation rules and error templates. Chapter 7 talks about the current trend in WPF development, the Model View View-Model (MVVM) framework. This is a well known pattern for connecting things interface to actions, and it is explained competently. A typical implementation is presented which also presents the command pattern used throughout WPF. A complete application using MVVM is presented from start to finish, including typical features such as undo. Style and layout is covered on chapter 8. Why/how to use styles, applying them automatically,  using the many types of triggers to change styles automatically, using Expression Blend behaviors and templates are all covered. Next chapter, 9, is about graphics and animations programming. It explains how to create shapes, transform common UI elements, apply special effects and perform simple animations. The following chapter, 10, is about creating custom controls, either by deriving from UserControl or from an existing control or framework element class, applying custom templates for changing the way the control looks. One useful example is a custom layout panel that arranges its children along a circumference. The final chapter, 11, is about multi-threading programming and how one can integrate it with WPF. Includes how to invoke methods and properties on WPF classes from threads other than the main UI, using background tasks and timers and even using the new C# 5.0 asynchronous operations. It’s an interesting book, like I said, mostly for newcomers. It provides a competent introduction to WPF, with examples that cover the most common scenarios and also give directions to more complex ones. I recommend it to everyone wishing to learn WPF.

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• Yet Another ASP.NET MVC CRUD Tutorial

  - by Ricardo Peres

  I know that I have not posted much on MVC, mostly because I don’t use it on my daily life, but since I find it so interesting, and since it is gaining such popularity, I will be talking about it much more. This time, it’s about the most basic of scenarios: CRUD. Although there are several ASP.NET MVC tutorials out there that cover ordinary CRUD operations, I couldn’t find any that would explain how we can have also AJAX, optimistic concurrency control and validation, using Entity Framework Code First, so I set out to write one! I won’t go into explaining what is MVC, Code First or optimistic concurrency control, or AJAX, I assume you are all familiar with these concepts by now. Let’s consider an hypothetical use case, products. For simplicity, we only want to be able to either view a single product or edit this product. First, we need our model: 1: public class Product 2: { 3: public Product() 4: { 5: this.Details = new HashSet<OrderDetail>(); 6: } 7:  8: [Required] 9: [StringLength(50)] 10: public String Name 11: { 12: get; 13: set; 14: } 15:  16: [Key] 17: [ScaffoldColumn(false)] 18: [DatabaseGenerated(DatabaseGeneratedOption.Identity)] 19: public Int32 ProductId 20: { 21: get; 22: set; 23: } 24:  25: [Required] 26: [Range(1, 100)] 27: public Decimal Price 28: { 29: get; 30: set; 31: } 32:  33: public virtual ISet<OrderDetail> Details 34: { 35: get; 36: protected set; 37: } 38:  39: [Timestamp] 40: [ScaffoldColumn(false)] 41: public Byte[] RowVersion 42: { 43: get; 44: set; 45: } 46: } Keep in mind that this is a simple scenario. Let’s see what we have: A class Product, that maps to a product record on the database; A product has a required (RequiredAttribute) Name property which can contain up to 50 characters (StringLengthAttribute); The product’s Price must be a decimal value between 1 and 100 (RangeAttribute); It contains a set of order details, for each time that it has been ordered, which we will not talk about (Details); The record’s primary key (mapped to property ProductId) comes from a SQL Server IDENTITY column generated by the database (KeyAttribute, DatabaseGeneratedAttribute); The table uses a SQL Server ROWVERSION (previously known as TIMESTAMP) column for optimistic concurrency control mapped to property RowVersion (TimestampAttribute). Then we will need a controller for viewing product details, which will located on folder ~/Controllers under the name ProductController: 1: public class ProductController : Controller 2: { 3: [HttpGet] 4: public ViewResult Get(Int32 id = 0) 5: { 6: if (id != 0) 7: { 8: using (ProductContext ctx = new ProductContext()) 9: { 10: return (this.View("Single", ctx.Products.Find(id) ?? new Product())); 11: } 12: } 13: else 14: { 15: return (this.View("Single", new Product())); 16: } 17: } 18: } If the requested product does not exist, or one was not requested at all, one with default values will be returned. I am using a view named Single to display the product’s details, more on that later. As you can see, it delegates the loading of products to an Entity Framework context, which is defined as: 1: public class ProductContext: DbContext 2: { 3: public DbSet<Product> Products 4: { 5: get; 6: set; 7: } 8: } Like I said before, I’ll keep it simple for now, only aggregate root Product is available. The controller will use the standard routes defined by the Visual Studio ASP.NET MVC 3 template: 1: routes.MapRoute( 2: "Default", // Route name 3: "{controller}/{action}/{id}", // URL with parameters 4: new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults 5: ); Next, we need a view for displaying the product details, let’s call it Single, and have it located under ~/Views/Product: 1: <%@ Page Language="C#" Inherits="System.Web.Mvc.ViewPage<Product>" %> 2: <!DOCTYPE html> 3:  4: <html> 5: <head runat="server"> 6: <title>Product</title> 7: <script src="/Scripts/jquery-1.7.2.js" type="text/javascript"></script> 1:  2: <script src="/Scripts/jquery-ui-1.8.19.js" type="text/javascript"> 1: </script> 2: <script src="/Scripts/jquery.unobtrusive-ajax.js" type="text/javascript"> 1: </script> 2: <script src="/Scripts/jquery.validate.js" type="text/javascript"> 1: </script> 2: <script src="/Scripts/jquery.validate.unobtrusive.js" type="text/javascript"> 1: </script> 2: <script type="text/javascript"> 3: function onFailure(error) 4: { 5: } 6:  7: function onComplete(ctx) 8: { 9: } 10:  11: </script> 8: </head> 9: <body> 10: <div> 11: <% 1: : this.Html.ValidationSummary(false) %> 12: <% 1: using (this.Ajax.BeginForm("Edit", "Product", new AjaxOptions{ HttpMethod = FormMethod.Post.ToString(), OnSuccess = "onSuccess", OnFailure = "onFailure" })) { %> 13: <% 1: : this.Html.EditorForModel() %> 14: <input type="submit" name="submit" value="Submit" /> 15: <% 1: } %> 16: </div> 17: </body> 18: </html> Yes… I am using ASPX syntax… sorry about that!   I implemented an editor template for the Product class, which must be located on the ~/Views/Shared/EditorTemplates folder as file Product.ascx: 1: <%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<Product>" %> 2: <div> 3: <%: this.Html.HiddenFor(model => model.ProductId) %> 4: <%: this.Html.HiddenFor(model => model.RowVersion) %> 5: <fieldset> 6: <legend>Product</legend> 7: <div class="editor-label"> 8: <%: this.Html.LabelFor(model => model.Name) %> 9: </div> 10: <div class="editor-field"> 11: <%: this.Html.TextBoxFor(model => model.Name) %> 12: <%: this.Html.ValidationMessageFor(model => model.Name) %> 13: </div> 14: <div class="editor-label"> 15: <%= this.Html.LabelFor(model => model.Price) %> 16: </div> 17: <div class="editor-field"> 18: <%= this.Html.TextBoxFor(model => model.Price) %> 19: <%: this.Html.ValidationMessageFor(model => model.Price) %> 20: </div> 21: </fieldset> 22: </div> One thing you’ll notice is, I am including both the ProductId and the RowVersion properties as hidden fields; they will come handy later or, so that we know what product and version we are editing. The other thing is the included JavaScript files: jQuery, jQuery UI and unobtrusive validations. Also, I am not using the Content extension method for translating relative URLs, because that way I would lose JavaScript intellisense for jQuery functions. OK, so, at this moment, I want to add support for AJAX and optimistic concurrency control. So I write a controller method like this: 1: [HttpPost] 2: [AjaxOnly] 3: [Authorize] 4: public JsonResult Edit(Product product) 5: { 6: if (this.TryValidateModel(product) == true) 7: { 8: using (BlogContext ctx = new BlogContext()) 9: { 10: Boolean success = false; 11:  12: ctx.Entry(product).State = (product.ProductId == 0) ? EntityState.Added : EntityState.Modified; 13:  14: try 15: { 16: success = (ctx.SaveChanges() == 1); 17: } 18: catch (DbUpdateConcurrencyException) 19: { 20: ctx.Entry(product).Reload(); 21: } 22:  23: return (this.Json(new { Success = success, ProductId = product.ProductId, RowVersion = Convert.ToBase64String(product.RowVersion) })); 24: } 25: } 26: else 27: { 28: return (this.Json(new { Success = false, ProductId = 0, RowVersion = String.Empty })); 29: } 30: } So, this method is only valid for HTTP POST requests (HttpPost), coming from AJAX (AjaxOnly, from MVC Futures), and from authenticated users (Authorize). It returns a JSON object, which is what you would normally use for AJAX requests, containing three properties: Success: a boolean flag; RowVersion: the current version of the ROWVERSION column as a Base-64 string; ProductId: the inserted product id, as coming from the database. If the product is new, it will be inserted into the database, and its primary key will be returned into the ProductId property. Success will be set to true; If a DbUpdateConcurrencyException occurs, it means that the value in the RowVersion property does not match the current ROWVERSION column value on the database, so the record must have been modified between the time that the page was loaded and the time we attempted to save the product. In this case, the controller just gets the new value from the database and returns it in the JSON object; Success will be false. Otherwise, it will be updated, and Success, ProductId and RowVersion will all have their values set accordingly. So let’s see how we can react to these situations on the client side. Specifically, we want to deal with these situations: The user is not logged in when the update/create request is made, perhaps the cookie expired; The optimistic concurrency check failed; All went well. So, let’s change our view: 1: <%@ Page Language="C#" Inherits="System.Web.Mvc.ViewPage<Product>" %> 2: <%@ Import Namespace="System.Web.Security" %> 3:  4: <!DOCTYPE html> 5:  6: <html> 7: <head runat="server"> 8: <title>Product</title> 9: <script src="/Scripts/jquery-1.7.2.js" type="text/javascript"></script> 1:  2: <script src="/Scripts/jquery-ui-1.8.19.js" type="text/javascript"> 1: </script> 2: <script src="/Scripts/jquery.unobtrusive-ajax.js" type="text/javascript"> 1: </script> 2: <script src="/Scripts/jquery.validate.js" type="text/javascript"> 1: </script> 2: <script src="/Scripts/jquery.validate.unobtrusive.js" type="text/javascript"> 1: </script> 2: <script type="text/javascript"> 3: function onFailure(error) 4: { 5: window.alert('An error occurred: ' + error); 6: } 7:  8: function onSuccess(ctx) 9: { 10: if (typeof (ctx.Success) != 'undefined') 11: { 12: $('input#ProductId').val(ctx.ProductId); 13: $('input#RowVersion').val(ctx.RowVersion); 14:  15: if (ctx.Success == false) 16: { 17: window.alert('An error occurred while updating the entity: it may have been modified by third parties. Please try again.'); 18: } 19: else 20: { 21: window.alert('Saved successfully'); 22: } 23: } 24: else 25: { 26: if (window.confirm('Not logged in. Login now?') == true) 27: { 28: document.location.href = '<%: FormsAuthentication.LoginUrl %>?ReturnURL=' + document.location.pathname; 29: } 30: } 31: } 32:  33: </script> 10: </head> 11: <body> 12: <div> 13: <% 1: : this.Html.ValidationSummary(false) %> 14: <% 1: using (this.Ajax.BeginForm("Edit", "Product", new AjaxOptions{ HttpMethod = FormMethod.Post.ToString(), OnSuccess = "onSuccess", OnFailure = "onFailure" })) { %> 15: <% 1: : this.Html.EditorForModel() %> 16: <input type="submit" name="submit" value="Submit" /> 17: <% 1: } %> 18: </div> 19: </body> 20: </html> The implementation of the onSuccess function first checks if the response contains a Success property, if not, the most likely cause is the request was redirected to the login page (using Forms Authentication), because it wasn’t authenticated, so we navigate there as well, keeping the reference to the current page. It then saves the current values of the ProductId and RowVersion properties to their respective hidden fields. They will be sent on each successive post and will be used in determining if the request is for adding a new product or to updating an existing one. The only thing missing is the ability to insert a new product, after inserting/editing an existing one, which can be easily achieved using this snippet: 1: <input type="button" value="New" onclick="$('input#ProductId').val('');$('input#RowVersion').val('');"/> And that’s it.

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• Generating PDF Files With iTextSharp

  - by Ricardo Peres

  I recently had the need to generate a PDF file containing a table where some of the cells included images. Of course, I used iTextSharp to do it. Because it has some obscure parts, I decided to publish a simplified version of the code I used. using iTextSharp; using iTextSharp.text; using iTextSharp.text.pdf; using iTextSharp.text.html; //... protected void OnGeneratePdfClick() { String text = "Multi\nline\ntext"; String name = "Some Name"; String number = "12345"; Int32 rows = 7; Int32 cols = 3; Single headerHeight = 47f; Single footerHeight = 45f; Single rowHeight = 107.4f; String pdfName = String.Format("Labels - {0}", name); PdfPTable table = new PdfPTable(3) { WidthPercentage = 100, HeaderRows = 1 }; PdfPCell headerCell = new PdfPCell(new Phrase("Header")) { Colspan = cols, FixedHeight = headerHeight, HorizontalAlignment = Element.ALIGN_CENTER, BorderWidth = 0f }; table.AddCell(headerCell); FontFactory.RegisterDirectory(@"C:\WINDOWS\Fonts"); //required for the Verdana font Font cellFont = FontFactory.GetFont("Verdana", 6f, Font.NORMAL); for (Int32 r = 0; r SyntaxHighlighter.config.clipboardSwf = 'http://alexgorbatchev.com/pub/sh/2.0.320/scripts/clipboard.swf'; SyntaxHighlighter.brushes.CSharp.aliases = ['c#', 'c-sharp', 'csharp']; SyntaxHighlighter.all();

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• Dynamic Paging and Sorting

  - by Ricardo Peres

  Since .NET 3.5 brought us LINQ and expressions, I became a great fan of these technologies. There are times, however, when strong typing cannot be used - for example, when you are developing an ObjectDataSource and you need to do paging having just a column name, a page index and a page size, so I set out to fix this. Yes, I know about Dynamic LINQ, and even talked on it previously, but there's no need to add this extra assembly. So, without further delay, here's the code, in both generic and non-generic versions: public static IList ApplyPagingAndSorting(IEnumerable enumerable, Type elementType, Int32 pageSize, Int32 pageIndex, params String [] orderByColumns) { MethodInfo asQueryableMethod = typeof(Queryable).GetMethods(BindingFlags.Static | BindingFlags.Public).Where(m = (m.Name == "AsQueryable") && (m.ContainsGenericParameters == false)).Single(); IQueryable query = (enumerable is IQueryable) ? (enumerable as IQueryable) : asQueryableMethod.Invoke(null, new Object [] { enumerable }) as IQueryable; if ((orderByColumns != null) && (orderByColumns.Length 0)) { PropertyInfo orderByProperty = elementType.GetProperty(orderByColumns [ 0 ]); MemberExpression member = Expression.MakeMemberAccess(Expression.Parameter(elementType, "n"), orderByProperty); LambdaExpression orderBy = Expression.Lambda(member, member.Expression as ParameterExpression); MethodInfo orderByMethod = typeof(Queryable).GetMethods(BindingFlags.Public | BindingFlags.Static).Where(m = m.Name == "OrderBy").ToArray() [ 0 ].MakeGenericMethod(elementType, orderByProperty.PropertyType); query = orderByMethod.Invoke(null, new Object [] { query, orderBy }) as IQueryable; if (orderByColumns.Length 1) { MethodInfo thenByMethod = typeof(Queryable).GetMethods(BindingFlags.Public | BindingFlags.Static).Where(m = m.Name == "ThenBy").ToArray() [ 0 ].MakeGenericMethod(elementType, orderByProperty.PropertyType); PropertyInfo thenByProperty = null; MemberExpression thenByMember = null; LambdaExpression thenBy = null; for (Int32 i = 1; i 0) { MethodInfo takeMethod = typeof(Queryable).GetMethod("Take", BindingFlags.Public | BindingFlags.Static).MakeGenericMethod(elementType); MethodInfo skipMethod = typeof(Queryable).GetMethod("Skip", BindingFlags.Public | BindingFlags.Static).MakeGenericMethod(elementType); query = skipMethod.Invoke(null, new Object [] { query, pageSize * pageIndex }) as IQueryable; query = takeMethod.Invoke(null, new Object [] { query, pageSize }) as IQueryable; } MethodInfo toListMethod = typeof(Enumerable).GetMethod("ToList", BindingFlags.Static | BindingFlags.Public).MakeGenericMethod(elementType); IList list = toListMethod.Invoke(null, new Object [] { query }) as IList; return (list); } public static List ApplyPagingAndSorting(IEnumerable enumerable, Int32 pageSize, Int32 pageIndex, params String [] orderByColumns) { return (ApplyPagingAndSorting(enumerable, typeof(T), pageSize, pageIndex, orderByColumns) as List); } List list = new List { new DateTime(2010, 1, 1), new DateTime(1999, 1, 12), new DateTime(1900, 10, 10), new DateTime(1900, 2, 20), new DateTime(2012, 5, 5), new DateTime(2012, 1, 20) }; List sortedList = ApplyPagingAndSorting(list, 3, 0, "Year", "Month", "Day"); SyntaxHighlighter.config.clipboardSwf = 'http://alexgorbatchev.com/pub/sh/2.0.320/scripts/clipboard.swf'; SyntaxHighlighter.brushes.CSharp.aliases = ['c#', 'c-sharp', 'csharp']; SyntaxHighlighter.all();

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• Why should you choose Oracle WebLogic 12c instead of JBoss EAP 6?

  - by Ricardo Ferreira

  In this post, I will cover some technical differences between Oracle WebLogic 12c and JBoss EAP 6, which was released a couple days ago from Red Hat. This article claims to help you in the evaluation of key points that you should consider when choosing for an Java EE application server. In the following sections, I will present to you some important aspects that most customers ask us when they are seriously evaluating for an middleware infrastructure, specially if you are considering JBoss for some reason. I would suggest that you keep the following question in mind while you are reading the points: "Why should I choose JBoss instead of WebLogic?" 1) Multi Datacenter Deployment and Clustering - D/R ("Disaster & Recovery") architecture support is embedded on the WebLogic Server 12c product. JBoss EAP 6 on the other hand has no direct D/R support included, Red Hat relies on third-part tools with higher prices. When you consider a middleware solution to host your business critical application, you should worry with every architectural aspect that are related with the solution. Fail-over support is one little aspect of a truly reliable solution. If you do not worry about D/R, your solution will not be reliable. Having said that, with Red Hat and JBoss EAP 6, you have this extra cost that will increase considerably the total cost of ownership of the solution. As we commonly hear from analysts, open-source are not so cheaper when you start seeing the big picture. - WebLogic Server 12c supports advanced LAN clustering, detection of death servers and have a common alert framework. JBoss EAP 6 on the other hand has limited LAN clustering support with no server death detection. They do not generate any alerts when servers goes down (only if you buy JBoss ON which is a separated technology, but until now does not support JBoss EAP 6) and manual intervention are required when servers goes down. In most cases, admin people must rely on "kill -9", "tail -f someFile.log" and "ps ax | grep java" commands to manage failures and clustering anomalies. - WebLogic Server 12c supports the concept of Node Manager, which is a separated process that runs on the physical | virtual servers that allows extend the administration of the cluster to WebLogic managed servers that are often distributed across multiple machines and geographic locations. JBoss EAP 6 on the other hand has no equivalent technology. Whole server instances must be managed individually. - WebLogic Server 12c Node Manager supports Coherence to boost performance when managing servers. JBoss EAP 6 on the other hand has no similar technology. There is no way to coordinate JBoss and infiniband instances provided by JBoss using high throughput and low latency protocols like InfiniBand. The Node Manager feature also allows another very important feature that JBoss EAP lacks: secure the administration. When using WebLogic Node Manager, all the administration tasks are sent to the managed servers in a secure tunel protected by a certificate, which means that the transport layer that separates the WebLogic administration console from the managed servers are secured by SSL. - WebLogic Server 12c are now integrated with OTD ("Oracle Traffic Director") which is a web server technology derived from the former Sun iPlanet Web Server. This software complements the web server support offered by OHS ("Oracle HTTP Server"). Using OTD, WebLogic instances are load-balanced by a high powerful software that knows how to handle SDP ("Socket Direct Protocol") over InfiniBand, which boost performance when used with engineered systems technologies like Oracle Exalogic Elastic Cloud. JBoss EAP 6 on the other hand only offers support to Apache Web Server with custom modules created to deal with JBoss clusters, but only across standard TCP/IP networks.  2) Application and Runtime Diagnostics - WebLogic Server 12c have diagnostics capabilities embedded on the server called WLDF ("WebLogic Diagnostic Framework") so there is no need to rely on third-part tools. JBoss EAP 6 on the other hand has no diagnostics capabilities. Their only diagnostics tool is the log generated by the application server. Admin people are encouraged to analyse thousands of log lines to find out what is going on. - WebLogic Server 12c complement WLDF with JRockit MC ("Mission Control"), which provides to administrators and developers a complete insight about the JVM performance, behavior and possible bottlenecks. WebLogic Server 12c also have an classloader analysis tool embedded, and even a log analyzer tool that enables administrators and developers to view logs of multiple servers at the same time. JBoss EAP 6 on the other hand relies on third-part tools to do something similar. Again, only log searching are offered to find out whats going on. - WebLogic Server 12c offers end-to-end traceability and monitoring available through Oracle EM ("Enterprise Manager"), including monitoring of business transactions that flows through web servers, ESBs, application servers and database servers, all of this with high deep JVM analysis and diagnostics. JBoss EAP 6 on the other hand, even using JBoss ON ("Operations Network"), which is a separated technology, does not support those features. Red Hat relies on third-part tools to provide direct Oracle database traceability across JVMs. One of those tools are Oracle EM for non-Oracle middleware that manage JBoss, Tomcat, Websphere and IIS transparently. - WebLogic Server 12c with their JRockit support offers a tool called JRockit Flight Recorder, which can give developers a complete visibility of a certain period of application production monitoring with zero extra overhead. This automatic recording allows you to deep analyse threads latency, memory leaks, thread contention, resource utilization, stack overflow damages and GC ("Garbage Collection") cycles, to observe in real time stop-the-world phenomenons, generational, reference count and parallel collects and mutator threads analysis. JBoss EAP 6 don't even dream to support something similar, even because they don't have their own JVM. 3) Application Server Administration - WebLogic Server 12c offers a complete administration console complemented with scripting and macro-like recording capabilities. A single WebLogic console can managed up to hundreds of WebLogic servers belonging to the same domain. JBoss EAP 6 on the other hand has a limited console and provides a XML centric administration. JBoss, after ten years, started the development of a rudimentary centralized administration that still leave a lot of administration tasks aside, so admin people and developers must touch scripts and XML configuration files for most advanced and even simple administration tasks. This lead applications to error prone and risky deployments. Even using JBoss ON, JBoss EAP are not able to offer decent administration features for admin people which must be high skilled in JBoss internal architecture and its managing capabilities. - Oracle EM is available to manage multiple domains, databases, application servers, operating systems and virtualization, with a complete end-to-end visibility. JBoss ON does not provide management capabilities across the complete architecture, only basic monitoring. Even deployment must be done aside JBoss ON which does no integrate well with others softwares than JBoss. Until now, JBoss ON does not supports JBoss EAP 6, so even their minimal support for JBoss are not available for JBoss EAP 6 leaving customers uncovered and subject to high skilled JBoss admin people. - WebLogic Server 12c has the same administration model whatever is the topology selected by the customer. JBoss EAP 6 on the other hand differentiates between two operational models: standalone-mode and domain-mode, that are not consistent with each other. Depending on the mode used, the administration skill is different. - WebLogic Server 12c has no point-of-failures processes, and it does not need to define any specialized server. Domain model in WebLogic is available for years (at least ten years or more) and is production proven. JBoss EAP 6 on the other hand needs special processes to garantee JBoss integrity, the PC ("Process-Controller") and the HC ("Host-Controller"). Different from WebLogic, the domain model in JBoss is quite new (one year at tops) of maturity, and need to mature considerably until start doing things like WebLogic domain model does. - WebLogic Server 12c supports parallel deployment model which enables some artifacts being deployed at the same time. JBoss EAP 6 on the other hand does not have any similar feature. Every deployment are done atomically in the containers. This means that if you have a huge EAR (an EAR of 120 MB of size for instance) and deploy onto JBoss EAP 6, this EAR will take some minutes in order to starting accept thread requests. The same EAR deployed onto WebLogic Server 12c will reduce the deployment time at least in 2X compared to JBoss. 4) Support and Upgrades - WebLogic Server 12c has patch management available. JBoss EAP 6 on the other hand has no patch management available, each JBoss EAP instance should be patched manually. To achieve such feature, you need to buy a separated technology called JBoss ON ("Operations Network") that manage this type of stuff. But until now, JBoss ON does not support JBoss EAP 6 so, in practice, JBoss EAP 6 does not have this feature. - WebLogic Server 12c supports previuous WebLogic domains without any reconfiguration since its kernel is robust and mature since its creation in 1995. JBoss EAP 6 on the other hand has a proven lack of supportability between JBoss AS 4, 5, 6 and 7. Different kernels and messaging engines were implemented in JBoss stack in the last five years reveling their incapacity to create a well architected and proven middleware technology. - WebLogic Server 12c has patch prescription based on customer configuration. JBoss EAP 6 on the other hand has no such capability. People need to create ticket supports and have their installations revised by Red Hat support guys to gain some patch prescription from them. - Oracle WebLogic Server independent of the version has 8 years of support of new patches and has lifetime release of existing patches beyond that. JBoss EAP 6 on the other hand provides patches for a specific application server version up to 5 years after the release date. JBoss EAP 4 and previous versions had only 4 years. A good question that Red Hat will argue to answer is: "what happens when you find issues after year 5"?  5) RAC ("Real Application Clusters") Support - WebLogic Server 12c ships with a specific JDBC driver to leverage Oracle RAC clustering capabilities (Fast-Application-Notification, Transaction Affinity, Fast-Connection-Failover, etc). Oracle JDBC thin driver are also available. JBoss EAP 6 on the other hand ships only the standard Oracle JDBC thin driver. Load balancing with Oracle RAC are not supported. Manual intervention in case of planned or unplanned RAC downtime are necessary. In JBoss EAP 6, situation does not reestablish automatically after downtime. - WebLogic Server 12c has a feature called Active GridLink for Oracle RAC which provides up to 3X performance on OLTP applications. This seamless integration between WebLogic and Oracle database enable more value added to critical business applications leveraging their investments in Oracle database technology and Oracle middleware. JBoss EAP 6 on the other hand has no performance gains at all, even when admin people implement some kind of connection-pooling tuning. - WebLogic Server 12c also supports transaction and web session affinity to the Oracle RAC, which provides aditional gains of performance. This is particularly interesting if you are creating a reliable solution that are distributed not only in an LAN cluster, but into a different data center. JBoss EAP 6 on the other hand has no such support. 6) Standards and Technology Support - WebLogic Server 12c is fully Java EE 6 compatible and production ready since december of 2011. JBoss EAP 6 on the other hand became fully compatible with Java EE 6 only in the community version after three months, and production ready only in a few days considering that this article was written in June of 2012. Red Hat says that they are the masters of innovation and technology proliferation, but compared with Oracle and even other proprietary vendors like IBM, they historically speaking are lazy to deliver the most newest technologies and standards adherence. - Oracle is the steward of Java, driving innovation into the platform from commercial and open-source vendors. Red Hat on the other hand does not have its own JVM and relies on third-part JVMs to complete their application server offer. 95% of Red Hat customers are using Oracle HotSpot as JVM, which means that without Oracle involvement, their support are limited exclusively to the application server layer and we all know that most problems are happens in the JVM layer. - WebLogic Server 12c supports natively JDK 7, which empower developers to explore the maximum of the Java platform productivity when writing code. This feature differentiate WebLogic from others application servers (except GlassFish that are also managed by Oracle) because the usage of JDK 7 introduce such remarkable productivity features like the "try-with-resources" enhancement, catching multiple exceptions with one try block, Strings in the switch statements, JVM improvements in terms of JDBC, I/O, networking, security, concurrency and of course, the most important feature of Java 7: native support for multiple non-Java languages. More features regarding JDK 7 can be found here. JBoss EAP 6 on the other hand does not support JDK 7 officially, they comment in their community version that "Java SE 7 can be used with JBoss 7" which does not gives you any guarantees of enterprise support for JDK 7. - Oracle WebLogic Server 12c supports integration with Spring framework allowing Spring applications to use WebLogic special transaction manager, exposing bean interfaces to WebLogic MBeans to take advantage of all WebLogic monitoring and administration advantages. JBoss EAP 6 on the other hand has no special integration with Spring. In fact, Red Hat offers a suspicious package called "JBoss Web Platform" that in theory supports Spring, but in practice this package does not offers any special integration. It is just a facility for Red Hat customers to have support from both JBoss and Spring technology using the same customer support. 7) Lightweight Development - Oracle WebLogic Server 12c and Oracle GlassFish are completely integrated and can share applications without any modifications. Starting with the 12c version, WebLogic now understands natively GlassFish deployment descriptors and specific configurations in order to offer you a truly and reliable migration path from a community Java EE application server to a enterprise middleware product like WebLogic. JBoss EAP 6 on the other hand has no support to natively reuse an existing (or still in development) application from JBoss AS community server. Users of JBoss suffer of critical issues during deployment time that includes: changing the libraries and dependencies of the application, patching the DTD or XSD deployment descriptors, refactoring of the application layers due classloading issues and anomalies, rebuilding of persistence, business and web layers due issues with "usage of the certified version of an certain dependency" or "frameworks that Red Hat potentially does not recommend" etc. If you have the culture or enterprise IT directive of developing Java EE applications using community middleware to in a certain future, transition to enterprise (supported by a vendor) middleware, Oracle WebLogic plus Oracle GlassFish offers you a more sustainable solution. - WebLogic Server 12c has a very light ZIP distribution (less than 165 MB). JBoss EAP 6 ZIP size is around 130 MB, together with JBoss ON you have more 100 MB resulting in a higher download footprint. This is particularly interesting if you plan to use automated setup of application server instances (for example, to rapidly setup a development or staging environment) using Maven or Hudson. - WebLogic Server 12c has a complete integration with Maven allowing developers to setup WebLogic domains with few commands. Tasks like downloading WebLogic, installation, domain creation, data sources deployment are completely integrated. JBoss EAP 6 on the other hand has a limited offer integration with those tools.  - WebLogic Server 12c has a startup mode called WLX that turns-off EJB, JMS and JCA containers leaving enabled only the web container with Java EE 6 web profile. JBoss EAP 6 on the other hand has no such feature, you need to disable manually the containers that you do not want to use. - WebLogic Server 12c supports fastswap, which enables you to change classes without redeployment. This is particularly interesting if you are developing patches for the application that is already deployed and you do not want to redeploy the entire application. This is the same behavior that most application servers offers to JSP pages, but with WebLogic Server 12c, you have the same feature for Java classes in general. JBoss EAP 6 on the other hand has no such support. Even JBoss EAP 5 does not support this until now. 8) JMS and Messaging - WebLogic Server 12c has a proven and high scalable JMS implementation since its initial release in 1995. JBoss EAP 6 on the other hand has a still immature technology called HornetQ, which was introduced in JBoss EAP 5 replacing everything that was implemented in the previous versions. Red Hat loves to introduce new technologies across JBoss versions, playing around with customers and their investments. And when they are asked about why they have changed the implementation and caused such a mess, their answer is always: "the previous implementation was inadequate and not aligned with the community strategy so we are creating a new a improved one". This Red Hat practice leads to uncomfortable investments that in a near future (sometimes less than a year) will be affected in someway. - WebLogic Server 12c has troubleshooting and monitoring features included on the WebLogic console and WLDF. JBoss EAP 6 on the other hand has no direct monitoring on the console, activity is reflected only on the logs, no debug logs available in case of JMS issues. - WebLogic Server 12c has extremely good performance and scalability. JBoss EAP 6 on the other hand has a JMS storage mechanism relying on Oracle database or MySQL. This means that if an issue in production happens and Red Hat affirms that an performance issue is happening due to database problems, they will not support you on the performance issue. They will orient you to call Oracle instead. - WebLogic Server 12c supports messaging enterprise features like SAF ("Store and Forward"), Distributed Queues/Topics and Foreign JMS providers support that leverage JMS implementations without compromise developer code making things completely transparent. JBoss EAP 6 on the other hand do not even dream to support such features. 9) Caching and Grid - Coherence, which is the leading and most mature data grid technology from Oracle, is available since early 2000 and was integrated with WebLogic in 2009. Coherence and WebLogic clusters can be both managed from WebLogic administrative console. Even Node Manager supports Coherence. JBoss on the other hand discontinued JBoss Cache, which was their caching implementation just like they did with the messaging implementation (JBossMQ) which was a issue for long term customers. JBoss EAP 6 ships InfiniSpan version 1.0 which is immature and lack a proven record of successful cases and reliability. - WebLogic Server 12c has a feature called ActiveCache which uses Coherence to, without any code changes, replicate HTTP sessions from both WebLogic and other application servers like JBoss, Tomcat, Websphere, GlassFish and even Microsoft IIS. JBoss EAP 6 on the other hand does have such support and even when they do in the future, they probably will support only their own application server. - Coherence can be used to manage both L1 and L2 cache levels, providing support to Oracle TopLink and others JPA compliant implementations, even Hibernate. JBoss EAP 6 and Infinispan on the other hand supports only Hibernate. And most important of all: Infinispan does not have any successful case of L1 or L2 caching level support using Hibernate, which lead us to reflect about its viability. 10) Performance - WebLogic Server 12c is certified with Oracle Exalogic Elastic Cloud and can run unchanged applications at this engineered system. This approach can benefit customers from Exalogic optimization's of both kernel and JVM layers to boost performance in terms of 10X for web, OLTP, JMS and grid applications. JBoss EAP 6 on the other hand has no investment on engineered systems: customers do not have the choice to deploy on a Java ultra fast system if their project becomes relevant and performance issues are detected. - WebLogic Server 12c maintains a performance gain across each new release: starting on WebLogic 5.1, the overall performance gain has been close to 4X, which close to a 20% gain release by release. JBoss on the other hand does not provide SPECJAppServer or SPECJEnterprise performance benchmarks. Their so called "performance gains" remains hidden in their customer environments, which lead us to think if it is true or not since we will never get access to those environments. - WebLogic Server 12c has industry performance benchmarks with submissions across platforms and configurations leading SPECJ. Oracle WebLogic leads SPECJAppServer performance in multiple categories, fitting all customer topologies like: dual-node, single-node, multi-node and multi-node with RAC. JBoss... again, does not provide any SPECJAppServer performance benchmarks. - WebLogic Server 12c has a feature called work manager which allows your application to embrace new performance levels based on critical resource utilization of the CPUs usage. Work managers prioritizes work and allocates threads based on an execution model that takes into account administrator-defined parameters and actual run-time performance and throughput. JBoss EAP 6 on the other hand has no compared feature and probably they never will. Not supporting such feature like work managers, JBoss EAP 6 forces admin people and specially developers to uncover performance gains in a intrusive way, rewriting the code and doing performance refactorings. 11) Professional Services Support - WebLogic Server 12c and any other technology sold by Oracle give customers the possibility of hire OCS ("Oracle Consulting Services") to manage critical scenarios, deployment assistance of new applications, high skilled consultancy of architecture, best practices and people allocation together with customer teams. All OCS services are available without any restrictions, having the customer bought software from Oracle or just starting their implementation before any acquisition. JBoss EAP 6 or Red Hat to be more specifically, only offers professional services if you buy subscriptions from them. If you are developing a new critical application for your business and need the help of Red Hat for a serious issue or architecture decision, they will probably say: "OK... I can help you but after you buy subscriptions from me". Red Hat also does not allows their professional services consultants to manage environments that uses community based software. They will probably force you to first buy a subscription, download their "enterprise" version and them, optionally hire their consultants. - Oracle provides you our university to educate your team into our technologies, including of course specialized trainings of WebLogic application server. At any time and location, you can hire Oracle to train your team so you get trustful knowledge according to your specific needs. Certifications for the products are also available if your technical people desire to differentiate themselves as professionals. Red Hat on the other hand have a limited pool of resources to train your team in their technologies. Basically they are selling training and certification for RHEL ("Red Hat Enterprise Linux") but if you demand more specialized training in JBoss middleware, they will probably connect you to some "certified" partner localized training since they are apparently discontinuing their education center, at least here in Brazil. They were not able to reproduce their success with RHEL education to their middleware division since they need first sell the subscriptions to after gives you specialized training. And again, they only offer you specialized training based on their enterprise version (EAP in the case of JBoss) which means that the courses will be a quite outdated. There are reports of developers that took official training's from Red Hat at this year (2012) and in a certain JBoss advanced course, Red Hat supposedly covered JBossMQ as the messaging subsystem, and even the printed material provided was based on JBossMQ since the training was created for JBoss EAP 4.3. 12) Encouraging Transparency without Ulterior Motives - WebLogic Server 12c like any other software from Oracle can be downloaded any time from anywhere, you should only possess an OTN ("Oracle Technology Network") credential and you can download any enterprise software how many times you want. And is not some kind of "trial" version. It is the official binaries that will be running for ever in your data center. Oracle does not encourages the usage of "specific versions" of our software. The binaries you buy from Oracle are the same binaries anyone in the world could download and use for testing and personal education. JBoss EAP 6 on the other hand are not available for download unless you buy a subscription and get access to the Red Hat enterprise repositories. If you need to test, learn or just start creating your application using Red Hat's middleware software, you should download it from the community website. You are not allowed to download the enterprise version that, according to Red Hat are more secure, reliable and robust. But no one of us want to start the development of a software with an unsecured, unreliable and not scalable middleware right? So what you do? You are "invited" by Red Hat to buy subscriptions from them to get access to the "cool" version of the software. - WebLogic Server 12c prices are publicly available in the Oracle website. If you want to know right now how much WebLogic will cost to your organization, just click here and get access to our price list. In the case of WebLogic, check out the "US Oracle Technology Commercial Price List". Oracle also encourages you to get in touch with a sales representative to discuss discounts that would make possible the investment into our technology. But you are not required to do this, only if you are interested in buying our technology or maybe you want to discuss some discount scenarios. JBoss EAP 6 on the other hand does not have its cost publicly available in Red Hat's website or in any other media, at least is not so easy to get such information. The only link you will possibly find in their website is a "Contact a Sales Representative" link. This is not a very good relationship between an customer and an vendor. This is not an example of transparency, mainly when the software are sold as open. In this situations, customers expects to see the software prices publicly available, so they can have the chance to decide, based on the existing features of the software, if the cost is fair or not. Conclusion Oracle WebLogic is the most mature, secure, reliable and scalable Java EE application server of the market, and have a proven record of success around the globe to prove it's majority. Don't lose the chance to discover today how WebLogic could fit your needs and sustain your global IT middleware strategy, no matter if your strategy are completely based on the Cloud or not.

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• ASP.NET Web Forms Extensibility: Providers

  - by Ricardo Peres

  Introduction This will be the first of a number of posts on ASP.NET extensibility. At this moment I don’t know exactly how many will be and I only know a couple of subjects that I want to talk about, so more will come in the next days. I have the sensation that the providers offered by ASP.NET are not widely know, although everyone uses, for example, sessions, they may not be aware of the extensibility points that Microsoft included. This post won’t go into details of how to configure and extend each of the providers, but will hopefully give some pointers on that direction. Canonical These are the most widely known and used providers, coming from ASP.NET 1, chances are, you have used them already. Good support for invoking client side, either from a .NET application or from JavaScript. Lots of server-side controls use them, such as the Login control for example. Membership The Membership provider is responsible for managing registered users, including creating new ones, authenticating them, changing passwords, etc. ASP.NET comes with two implementations, one that uses a SQL Server database and another that uses the Active Directory. The base class is Membership and new providers are registered on the membership section on the Web.config file, as well as parameters for specifying minimum password lengths, complexities, maximum age, etc. One reason for creating a custom provider would be, for example, storing membership information in a different database engine. 1: <membership defaultProvider="MyProvider"> 2: <providers> 3: <add name="MyProvider" type="MyClass, MyAssembly"/> 4: </providers> 5: </membership> Role The Role provider assigns roles to authenticated users. The base class is Role and there are three out of the box implementations: XML-based, SQL Server and Windows-based. Also registered on Web.config through the roleManager section, where you can also say if your roles should be cached on a cookie. If you want your roles to come from a different place, implement a custom provider. 1: <roleManager defaultProvider="MyProvider"> 2: <providers> 3: <add name="MyProvider" type="MyClass, MyAssembly" /> 4: </providers> 5: </roleManager> Profile The Profile provider allows defining a set of properties that will be tied and made available to authenticated or even anonymous ones, which must be tracked by using anonymous authentication. The base class is Profile and the only included implementation stores these settings in a SQL Server database. Configured through profile section, where you also specify the properties to make available, a custom provider would allow storing these properties in different locations. 1: <profile defaultProvider="MyProvider"> 2: <providers> 3: <add name="MyProvider" type="MyClass, MyAssembly"/> 4: </providers> 5: </profile> Basic OK, I didn’t know what to call these, so Basic is probably as good as a name as anything else. Not supported client-side (doesn’t even make sense). Session The Session provider allows storing data tied to the current “session”, which is normally created when a user first accesses the site, even when it is not yet authenticated, and remains all the way. The base class and only included implementation is SessionStateStoreProviderBase and it is capable of storing data in one of three locations: In the process memory (default, not suitable for web farms or increased reliability); A SQL Server database (best for reliability and clustering); The ASP.NET State Service, which is a Windows Service that is installed with the .NET Framework (ok for clustering). The configuration is made through the sessionState section. By adding a custom Session provider, you can store the data in different locations – think for example of a distributed cache. 1: <sessionState customProvider=”MyProvider”> 2: <providers> 3: <add name=”MyProvider” type=”MyClass, MyAssembly” /> 4: </providers> 5: </sessionState> Resource A not so known provider, allows you to change the origin of localized resource elements. By default, these come from RESX files and are used whenever you use the Resources expression builder or the GetGlobalResourceObject and GetLocalResourceObject methods, but if you implement a custom provider, you can have these elements come from some place else, such as a database. The base class is ResourceProviderFactory and there’s only one internal implementation which uses these RESX files. Configuration is through the globalization section. 1: <globalization resourceProviderFactoryType="MyClass, MyAssembly" /> Health Monitoring Health Monitoring is also probably not so well known, and actually not a good name for it. First, in order to understand what it does, you have to know that ASP.NET fires “events” at specific times and when specific things happen, such as when logging in, an exception is raised. These are not user interface events and you can create your own and fire them, nothing will happen, but the Health Monitoring provider will detect it. You can configure it to do things when certain conditions are met, such as a number of events being fired in a certain amount of time. You define these rules and route them to a specific provider, which must inherit from WebEventProvider. Out of the box implementations include sending mails, logging to a SQL Server database, writing to the Windows Event Log, Windows Management Instrumentation, the IIS 7 Trace infrastructure or the debugger Trace. Its configuration is achieved by the healthMonitoring section and a reason for implementing a custom provider would be, for example, locking down a web application in the event of a significant number of failed login attempts occurring in a small period of time. 1: <healthMonitoring> 2: <providers> 3: <add name="MyProvider" type="MyClass, MyAssembly"/> 4: </providers> 5: </healthMonitoring> Sitemap The Sitemap provider allows defining the site’s navigation structure and associated required permissions for each node, in a tree-like fashion. Usually this is statically defined, and the included provider allows it, by supplying this structure in a Web.sitemap XML file. The base class is SiteMapProvider and you can extend it in order to supply you own source for the site’s structure, which may even be dynamic. Its configuration must be done through the siteMap section. 1: <siteMap defaultProvider="MyProvider"> 2: <providers><add name="MyProvider" type="MyClass, MyAssembly" /> 3: </providers> 4: </siteMap> Web Part Personalization Web Parts are better known by SharePoint users, but since ASP.NET 2.0 they are included in the core Framework. Web Parts are server-side controls that offer certain possibilities of configuration by clients visiting the page where they are located. The infrastructure handles this configuration per user or globally for all users and this provider is responsible for just that. The base class is PersonalizationProvider and the only included implementation stores settings on SQL Server. Add new providers through the personalization section. 1: <webParts> 2: <personalization defaultProvider="MyProvider"> 3: <providers> 4: <add name="MyProvider" type="MyClass, MyAssembly"/> 5: </providers> 6: </personalization> 7: </webParts> Build The Build provider is responsible for compiling whatever files are present on your web folder. There’s a base class, BuildProvider, and, as can be expected, internal implementations for building pages (ASPX), master pages (Master), user web controls (ASCX), handlers (ASHX), themes (Skin), XML Schemas (XSD), web services (ASMX, SVC), resources (RESX), browser capabilities files (Browser) and so on. You would write a build provider if you wanted to generate code from any kind of non-code file so that you have strong typing at development time. Configuration goes on the buildProviders section and it is per extension. 1: <buildProviders> 2: <add extension=".ext" type="MyClass, MyAssembly” /> 3: </buildProviders> New in ASP.NET 4 Not exactly new since they exist since 2010, but in ASP.NET terms, still new. Output Cache The Output Cache for ASPX pages and ASCX user controls is now extensible, through the Output Cache provider, which means you can implement a custom mechanism for storing and retrieving cached data, for example, in a distributed fashion. The base class is OutputCacheProvider and the only implementation is private. Configuration goes on the outputCache section and on each page and web user control you can choose the provider you want to use. 1: <caching> 2: <outputCache defaultProvider="MyProvider"> 3: <providers> 4: <add name="MyProvider" type="MyClass, MyAssembly"/> 5: </providers> 6: </outputCache> 7: </caching> Request Validation A big change introduced in ASP.NET 4 (and refined in 4.5, by the way) is the introduction of extensible request validation, by means of a Request Validation provider. This means we are not limited to either enabling or disabling event validation for all pages or for a specific page, but we now have fine control over each of the elements of the request, including cookies, headers, query string and form values. The base provider class is RequestValidator and the configuration goes on the httpRuntime section. 1: <httpRuntime requestValidationType="MyClass, MyAssembly" /> Browser Capabilities The Browser Capabilities provider is new in ASP.NET 4, although the concept exists from ASP.NET 2. The idea is to map a browser brand and version to its supported capabilities, such as JavaScript version, Flash support, ActiveX support, and so on. Previously, this was all hardcoded in .Browser files located in %WINDIR%\Microsoft.NET\Framework(64)\vXXXXX\Config\Browsers, but now you can have a class inherit from HttpCapabilitiesProvider and implement your own mechanism. Register in on the browserCaps section. 1: <browserCaps provider="MyClass, MyAssembly" /> Encoder The Encoder provider is responsible for encoding every string that is sent to the browser on a page or header. This includes for example converting special characters for their standard codes and is implemented by the base class HttpEncoder. Another implementation takes care of Anti Cross Site Scripting (XSS) attacks. Build your own by inheriting from one of these classes if you want to add some additional processing to these strings. The configuration will go on the httpRuntime section. 1: <httpRuntime encoderType="MyClass, MyAssembly" /> Conclusion That’s about it for ASP.NET providers. It was by no means a thorough description, but I hope I managed to raise your interest on this subject. There are lots of pointers on the Internet, so I only included direct references to the Framework classes and configuration sections. Stay tuned for more extensibility!

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• Loading a Template From a User Control

  - by Ricardo Peres

  What if you wanted to load a template (ITemplate property) from an external user control (.ascx) file? Yes, it is possible; there are a number of ways to do this, the one I'll talk about here is through a type converter. You need to apply a TypeConverterAttribute to your ITemplate property where you specify a custom type converter that does the job. This type converter relies on InstanceDescriptor. Here is the code for it: public class TemplateTypeConverter: TypeConverter { public override Boolean CanConvertFrom(ITypeDescriptorContext context, Type sourceType) { return ((sourceType == typeof(String)) || (base.CanConvertFrom(context, sourceType) == true)); } public override Boolean CanConvertTo(ITypeDescriptorContext context, Type destinationType) { return ((destinationType == typeof(InstanceDescriptor)) || (base.CanConvertTo(context, destinationType) == true)); } public override Object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, Object value, Type destinationType) { if (destinationType == typeof(InstanceDescriptor)) { Object objectFactory = value.GetType().GetField("_objectFactory", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(value); Object builtType = objectFactory.GetType().BaseType.GetField("_builtType", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(objectFactory); MethodInfo loadTemplate = typeof(TemplateTypeConverter).GetMethod("LoadTemplate"); return (new InstanceDescriptor(loadTemplate, new Object [] { "~/" + (builtType as Type).Name.Replace('_', '/').Replace("/ascx", ".ascx") })); } return base.ConvertTo(context, culture, value, destinationType); } public static ITemplate LoadTemplate(String virtualPath) { using (Page page = new Page()) { return (page.LoadTemplate(virtualPath)); } } } And, on your control: public class MyControl: Control { [Browsable(false)] [TypeConverter(typeof(TemplateTypeConverter))] public ITemplate Template { get; set; } } This allows the following declaration: Hope this helps! SyntaxHighlighter.config.clipboardSwf = 'http://alexgorbatchev.com/pub/sh/2.0.320/scripts/clipboard.swf'; SyntaxHighlighter.brushes.CSharp.aliases = ['c#', 'c-sharp', 'csharp']; SyntaxHighlighter.brushes.Xml.aliases = ['xml']; SyntaxHighlighter.all();

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• ASP.NET MVC Validation Complete

  - by Ricardo Peres

  OK, so let’s talk about validation. Most people are probably familiar with the out of the box validation attributes that MVC knows about, from the System.ComponentModel.DataAnnotations namespace, such as EnumDataTypeAttribute, RequiredAttribute, StringLengthAttribute, RangeAttribute, RegularExpressionAttribute and CompareAttribute from the System.Web.Mvc namespace. All of these validators inherit from ValidationAttribute and perform server as well as client-side validation. In order to use them, you must include the JavaScript files MicrosoftMvcValidation.js, jquery.validate.js or jquery.validate.unobtrusive.js, depending on whether you want to use Microsoft’s own library or jQuery. No significant difference exists, but jQuery is more extensible. You can also create your own attribute by inheriting from ValidationAttribute, but, if you want to have client-side behavior, you must also implement IClientValidatable (all of the out of the box validation attributes implement it) and supply your own JavaScript validation function that mimics its server-side counterpart. Of course, you must reference the JavaScript file where the declaration function is. Let’s see an example, validating even numbers. First, the validation attribute: 1: [Serializable] 2: [AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = true)] 3: public class IsEvenAttribute : ValidationAttribute, IClientValidatable 4: { 5: protected override ValidationResult IsValid(Object value, ValidationContext validationContext) 6: { 7: Int32 v = Convert.ToInt32(value); 8:  9: if (v % 2 == 0) 10: { 11: return (ValidationResult.Success); 12: } 13: else 14: { 15: return (new ValidationResult("Value is not even")); 16: } 17: } 18:  19: #region IClientValidatable Members 20:  21: public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context) 22: { 23: yield return (new ModelClientValidationRule() { ValidationType = "iseven", ErrorMessage = "Value is not even" }); 24: } 25:  26: #endregion 27: } The iseven validation function is declared like this in JavaScript, using jQuery validation: 1: jQuery.validator.addMethod('iseven', function (value, element, params) 2: { 3: return (true); 4: return ((parseInt(value) % 2) == 0); 5: }); 6:  7: jQuery.validator.unobtrusive.adapters.add('iseven', [], function (options) 8: { 9: options.rules['iseven'] = options.params; 10: options.messages['iseven'] = options.message; 11: }); Do keep in mind that this is a simple example, for example, we are not using parameters, which may be required for some more advanced scenarios. As a side note, if you implement a custom validator that also requires a JavaScript function, you’ll probably want them together. One way to achieve this is by including the JavaScript file as an embedded resource on the same assembly where the custom attribute is declared. You do this by having its Build Action set as Embedded Resource inside Visual Studio: Then you have to declare an attribute at assembly level, perhaps in the AssemblyInfo.cs file: 1: [assembly: WebResource("SomeNamespace.IsEven.js", "text/javascript")] In your views, if you want to include a JavaScript file from an embedded resource you can use this code: 1: public static class UrlExtensions 2: { 3: private static readonly MethodInfo getResourceUrlMethod = typeof(AssemblyResourceLoader).GetMethod("GetWebResourceUrlInternal", BindingFlags.NonPublic | BindingFlags.Static); 4:  5: public static IHtmlString Resource<TType>(this UrlHelper url, String resourceName) 6: { 7: return (Resource(url, typeof(TType).Assembly.FullName, resourceName)); 8: } 9:  10: public static IHtmlString Resource(this UrlHelper url, String assemblyName, String resourceName) 11: { 12: String resourceUrl = getResourceUrlMethod.Invoke(null, new Object[] { Assembly.Load(assemblyName), resourceName, false, false, null }).ToString(); 13: return (new HtmlString(resourceUrl)); 14: } 15: } And on the view: 1: <script src="<%: this.Url.Resource("SomeAssembly", "SomeNamespace.IsEven.js") %>" type="text/javascript"></script> Then there’s the CustomValidationAttribute. It allows externalizing your validation logic to another class, so you have to tell which type and method to use. The method can be static as well as instance, if it is instance, the class cannot be abstract and must have a public parameterless constructor. It can be applied to a property as well as a class. It does not, however, support client-side validation. Let’s see an example declaration: 1: [CustomValidation(typeof(ProductValidator), "OnValidateName")] 2: public String Name 3: { 4: get; 5: set; 6: } The validation method needs this signature: 1: public static ValidationResult OnValidateName(String name) 2: { 3: if ((String.IsNullOrWhiteSpace(name) == false) && (name.Length <= 50)) 4: { 5: return (ValidationResult.Success); 6: } 7: else 8: { 9: return (new ValidationResult(String.Format("The name has an invalid value: {0}", name), new String[] { "Name" })); 10: } 11: } Note that it can be either static or instance and it must return a ValidationResult-derived class. ValidationResult.Success is null, so any non-null value is considered a validation error. The single method argument must match the property type to which the attribute is attached to or the class, in case it is applied to a class: 1: [CustomValidation(typeof(ProductValidator), "OnValidateProduct")] 2: public class Product 3: { 4: } The signature must thus be: 1: public static ValidationResult OnValidateProduct(Product product) 2: { 3: } Continuing with attribute-based validation, another possibility is RemoteAttribute. This allows specifying a controller and an action method just for performing the validation of a property or set of properties. This works in a client-side AJAX way and it can be very useful. Let’s see an example, starting with the attribute declaration and proceeding to the action method implementation: 1: [Remote("Validate", "Validation")] 2: public String Username 3: { 4: get; 5: set; 6: } The controller action method must contain an argument that can be bound to the property: 1: public ActionResult Validate(String username) 2: { 3: return (this.Json(true, JsonRequestBehavior.AllowGet)); 4: } If in your result JSON object you include a string instead of the true value, it will consider it as an error, and the validation will fail. This string will be displayed as the error message, if you have included it in your view. You can also use the remote validation approach for validating your entire entity, by including all of its properties as included fields in the attribute and having an action method that receives an entity instead of a single property: 1: [Remote("Validate", "Validation", AdditionalFields = "Price")] 2: public String Name 3: { 4: get; 5: set; 6: } 7:  8: public Decimal Price 9: { 10: get; 11: set; 12: } The action method will then be: 1: public ActionResult Validate(Product product) 2: { 3: return (this.Json("Product is not valid", JsonRequestBehavior.AllowGet)); 4: } Only the property to which the attribute is applied and the additional properties referenced by the AdditionalFields will be populated in the entity instance received by the validation method. The same rule previously stated applies, if you return anything other than true, it will be used as the validation error message for the entity. The remote validation is triggered automatically, but you can also call it explicitly. In the next example, I am causing the full entity validation, see the call to serialize(): 1: function validate() 2: { 3: var form = $('form'); 4: var data = form.serialize(); 5: var url = '<%: this.Url.Action("Validation", "Validate") %>'; 6:  7: var result = $.ajax 8: ( 9: { 10: type: 'POST', 11: url: url, 12: data: data, 13: async: false 14: } 15: ).responseText; 16:  17: if (result) 18: { 19: //error 20: } 21: } Finally, by implementing IValidatableObject, you can implement your validation logic on the object itself, that is, you make it self-validatable. This will only work server-side, that is, the ModelState.IsValid property will be set to false on the controller’s action method if the validation in unsuccessful. Let’s see how to implement it: 1: public class Product : IValidatableObject 2: { 3: public String Name 4: { 5: get; 6: set; 7: } 8:  9: public Decimal Price 10: { 11: get; 12: set; 13: } 14:  15: #region IValidatableObject Members 16: 17: public IEnumerable<ValidationResult> Validate(ValidationContext validationContext) 18: { 19: if ((String.IsNullOrWhiteSpace(this.Name) == true) || (this.Name.Length > 50)) 20: { 21: yield return (new ValidationResult(String.Format("The name has an invalid value: {0}", this.Name), new String[] { "Name" })); 22: } 23: 24: if ((this.Price <= 0) || (this.Price > 100)) 25: { 26: yield return (new ValidationResult(String.Format("The price has an invalid value: {0}", this.Price), new String[] { "Price" })); 27: } 28: } 29: 30: #endregion 31: } The errors returned will be matched against the model properties through the MemberNames property of the ValidationResult class and will be displayed in their proper labels, if present on the view. On the controller action method you can check for model validity by looking at ModelState.IsValid and you can get actual error messages and related properties by examining all of the entries in the ModelState dictionary: 1: Dictionary<String, String> errors = new Dictionary<String, String>(); 2:  3: foreach (KeyValuePair<String, ModelState> keyValue in this.ModelState) 4: { 5: String key = keyValue.Key; 6: ModelState modelState = keyValue.Value; 7:  8: foreach (ModelError error in modelState.Errors) 9: { 10: errors[key] = error.ErrorMessage; 11: } 12: } And these are the ways to perform date validation in ASP.NET MVC. Don’t forget to use them!

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• Microsoft Developer Training Kits

  - by Ricardo Peres

  Here's a personal list of some of Microsoft's available and updated developer training kits: PHP on Windows Training Kit: http://www.microsoft.com/downloads/details.aspx?displaylang=en&familyid=c8498c9b-a85a-4afa-90c0-593d0e4850cb Identity Developer Training Kit: http://www.microsoft.com/downloads/details.aspx?familyid=C3E315FA-94E2-4028-99CB-904369F177C0&displaylang=en Office 2010 Developer Training Kit: http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=f1599288-a99f-410f-a219-f4375dbe310c SharePoint 2010 Developer Training Kit: http://www.microsoft.com/downloads/details.aspx?FamilyID=bfd1603b-7550-4b8e-be85-4215a5069b90 Silverlight 4 Training: http://www.microsoft.com/downloads/details.aspx?FamilyID=24cea29e-042e-41c9-aa16-684a0ca5f5db SQL Server 2008 R2 Training Kit (includes SQL Server 2008): http://www.microsoft.com/downloads/details.aspx?FamilyID=fffaad6a-0153-4d41-b289-a3ed1d637c0d Visual Studio 2010 and .NET Framework 4 Training Kit: http://www.microsoft.com/downloads/details.aspx?FamilyID=752cb725-969b-4732-a383-ed5740f02e93 Windows Server 2008 R2 Developer Training Kit: http://www.microsoft.com/downloads/details.aspx?FamilyID=c48b3eb4-ad4b-461c-9d5a-25f45d949b92&displaylang=en Windows 7 Training Kit For Developers: http://www.microsoft.com/downloads/details.aspx?familyid=1C333F06-FADB-4D93-9C80-402621C600E7&displaylang=en Windows Phone 7 Training Kit for Developers: http://www.microsoft.com/downloads/details.aspx?familyid=CA23285F-BAB8-47FA-B364-11553E076A9A&displaylang=en Windows Mobile 6.5 Developer Tool Kit: http://www.microsoft.com/downloads/details.aspx?familyid=20686A1D-97A8-4F80-BC6A-AE010E085A6E&displaylang=en

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• NHibernate 2 Beginner's Guide Book

  - by Ricardo Peres

  Packt Publishing has recently released a new book on NHibernate: NHibernate 2 Beginner's Guide, by Aaron Cure. I am now reading the final version, which Packt Publishing was kind enough to provide me, and I will soon write about it. I can tell you for now that Fabio Maulo was one of the reviewers, which certainly raises the expectations. In the meanwhile, there's a free chapter you can download, which hopefully will get you interested in it; you can get it from here.

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• Initially Unselected DropDownList

  - by Ricardo Peres

  One of the most (IMHO) things with DropDownList is its inability to show an unselected value at load time, which is something that HTML does permit. I decided to change the DropDownList to add this behavior. All was needed was some JavaScript and reflection. See the result for yourself: public class CustomDropDownList : DropDownList { public CustomDropDownList() { this.InitiallyUnselected = true; } [DefaultValue(true)] public Boolean InitiallyUnselected { get; set; } protected override void OnInit(EventArgs e) { this.Page.RegisterRequiresControlState(this); this.Page.PreRenderComplete += this.OnPreRenderComplete; base.OnInit(e); } protected virtual void OnPreRenderComplete(Object sender, EventArgs args) { FieldInfo cachedSelectedValue = typeof(ListControl).GetField("cachedSelectedValue", BindingFlags.NonPublic | BindingFlags.Instance); if (String.IsNullOrEmpty(cachedSelectedValue.GetValue(this) as String) == true) { if (this.InitiallyUnselected == true) { if ((ScriptManager.GetCurrent(this.Page) != null) && (ScriptManager.GetCurrent(this.Page).IsInAsyncPostBack == true)) { ScriptManager.RegisterStartupScript(this, this.GetType(), "unselect" + this.ClientID, "$get('" + this.ClientID + "').selectedIndex = -1;", true); } else { this.Page.ClientScript.RegisterStartupScript(this.GetType(), "unselect" + this.ClientID, "$get('" + this.ClientID + "').selectedIndex = -1;", true); } } } } } SyntaxHighlighter.config.clipboardSwf = 'http://alexgorbatchev.com/pub/sh/2.0.320/scripts/clipboard.swf'; SyntaxHighlighter.brushes.CSharp.aliases = ['c#', 'c-sharp', 'csharp']; SyntaxHighlighter.all();

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• ASP.NET List Control

  - by Ricardo Peres

  Today I developed a simple control for generating lists in ASP.NET, something that the base class library does not contain; it allows for nested lists where the list item types and images can be configured on a list by list basis. Since it was a great fun to develop, I'd like to share it here. Here is the code: [ParseChildren(true)] [PersistChildren(false)] public class List: WebControl { public List(): base("ul") { this.Items = new List(); this.ListStyleType = ListStyleType.Auto; this.ListStyleImageUrl = String.Empty; this.CommonCssClass = String.Empty; this.ContainerCssClass = String.Empty; } [DefaultValue(ListStyleType.Auto)] public ListStyleType ListStyleType { get; set; } [DefaultValue("")] [UrlProperty("*.png;*.gif;*.jpg")] public String ListStyleImageUrl { get; set; } [DefaultValue("")] [CssClassProperty] public String CommonCssClass { get; set; } [DefaultValue("")] [CssClassProperty] public String ContainerCssClass { get; set; } [Browsable(false)] [PersistenceModeAttribute(PersistenceMode.InnerProperty)] public List Items { private set; get; } protected override void Render(HtmlTextWriter writer) { String cssClass = String.Join(" ", new String [] { this.CssClass, this.ContainerCssClass }); if (cssClass.Trim().Length != 0) { this.CssClass = cssClass; } if (String.IsNullOrEmpty(this.ListStyleImageUrl) == false) { this.Style[ HtmlTextWriterStyle.ListStyleImage ] = String.Format("url('{0}')", this.ResolveClientUrl(this.ListStyleImageUrl)); } if (this.ListStyleType != ListStyleType.Auto) { switch (this.ListStyleType) { case ListStyleType.Circle: case ListStyleType.Decimal: case ListStyleType.Disc: case ListStyleType.None: case ListStyleType.Square: this.Style [ HtmlTextWriterStyle.ListStyleType ] = this.ListStyleType.ToString().ToLower(); break; case ListStyleType.LowerAlpha: this.Style [ HtmlTextWriterStyle.ListStyleType ] = "lower-alpha"; break; case ListStyleType.LowerRoman: this.Style [ HtmlTextWriterStyle.ListStyleType ] = "lower-roman"; break; case ListStyleType.UpperAlpha: this.Style [ HtmlTextWriterStyle.ListStyleType ] = "upper-alpha"; break; case ListStyleType.UpperRoman: this.Style [ HtmlTextWriterStyle.ListStyleType ] = "upper-roman"; break; } } base.Render(writer); } protected override void RenderChildren(HtmlTextWriter writer) { foreach (ListItem item in this.Items) { this.writeItem(item, this, 0); } base.RenderChildren(writer); } private void writeItem(ListItem item, Control control, Int32 depth) { HtmlGenericControl li = new HtmlGenericControl("li"); control.Controls.Add(li); if (String.IsNullOrEmpty(this.CommonCssClass) == false) { String cssClass = String.Join(" ", new String [] { this.CommonCssClass, this.CommonCssClass + depth }); li.Attributes [ "class" ] = cssClass; } foreach (String key in item.Attributes.Keys) { li.Attributes[key] = item.Attributes [ key ]; } li.InnerText = item.Text; if (item.ChildItems.Count != 0) { HtmlGenericControl ul = new HtmlGenericControl("ul"); li.Controls.Add(ul); if (String.IsNullOrEmpty(this.ContainerCssClass) == false) { ul.Attributes["class"] = this.ContainerCssClass; } if ((item.ListStyleType != ListStyleType.Auto) || (String.IsNullOrEmpty(item.ListStyleImageUrl) == false)) { if (String.IsNullOrEmpty(item.ListStyleImageUrl) == false) { ul.Style[HtmlTextWriterStyle.ListStyleImage] = String.Format("url('{0}');", this.ResolveClientUrl(item.ListStyleImageUrl)); } if (item.ListStyleType != ListStyleType.Auto) { switch (this.ListStyleType) { case ListStyleType.Circle: case ListStyleType.Decimal: case ListStyleType.Disc: case ListStyleType.None: case ListStyleType.Square: ul.Style[ HtmlTextWriterStyle.ListStyleType ] = item.ListStyleType.ToString().ToLower(); break; case ListStyleType.LowerAlpha: ul.Style [ HtmlTextWriterStyle.ListStyleType ] = "lower-alpha"; break; case ListStyleType.LowerRoman: ul.Style [ HtmlTextWriterStyle.ListStyleType ] = "lower-roman"; break; case ListStyleType.UpperAlpha: ul.Style [ HtmlTextWriterStyle.ListStyleType ] = "upper-alpha"; break; case ListStyleType.UpperRoman: ul.Style [ HtmlTextWriterStyle.ListStyleType ] = "upper-roman"; break; } } } foreach (ListItem childItem in item.ChildItems) { this.writeItem(childItem, ul, depth + 1); } } } } [Serializable] [ParseChildren(true, "ChildItems")] public class ListItem: IAttributeAccessor { public ListItem() { this.ChildItems = new List(); this.Attributes = new Dictionary(); this.Text = String.Empty; this.Value = String.Empty; this.ListStyleType = ListStyleType.Auto; this.ListStyleImageUrl = String.Empty; } [DefaultValue(ListStyleType.Auto)] public ListStyleType ListStyleType { get; set; } [DefaultValue("")] [UrlProperty("*.png;*.gif;*.jpg")] public String ListStyleImageUrl { get; set; } [DefaultValue("")] public String Text { get; set; } [DefaultValue("")] public String Value { get; set; } [Browsable(false)] public List ChildItems { get; private set; } [Browsable(false)] public Dictionary Attributes { get; private set; } String IAttributeAccessor.GetAttribute(String key) { return (this.Attributes [ key ]); } void IAttributeAccessor.SetAttribute(String key, String value) { this.Attributes [ key ] = value; } } [Serializable] public enum ListStyleType { Auto = 0, Disc, Circle, Square, Decimal, LowerRoman, UpperRoman, LowerAlpha, UpperAlpha, None } SyntaxHighlighter.config.clipboardSwf = 'http://alexgorbatchev.com/pub/sh/2.0.320/scripts/clipboard.swf'; SyntaxHighlighter.brushes.CSharp.aliases = ['c#', 'c-sharp', 'csharp']; SyntaxHighlighter.all();

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• NHibernate Tools

  - by Ricardo Peres

  Felice Pollano is the author of a two great new tools for working with NHibernate: NH Workbench: an IDE for writing HQL queries against a model db2hbm: generation of .hbm.xml files from a database (currently only SQL Server, more to come) I suggest you give them a try and give Felix your feedback!

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• NHibernate Pitfalls: Fetch and Paging

  - by Ricardo Peres

  This is part of a series of posts about NHibernate Pitfalls. See the entire collection here. NHibernate allows you to force loading additional references (many to one, one to one) or collections (one to many, many to many) in a query. You must know, however, that this is incompatible with paging. It’s easy to see why. Let’s say you want to get 5 products starting on the fifth, you can issue the following LINQ query: 1: session.Query<Product>().Take(5).Skip(5).ToList(); Will product this SQL in SQL Server: 1: SELECT 2: TOP (@p0) product1_4_, 3: name4_, 4: price4_ 5: FROM 6: (select 7: product0_.product_id as product1_4_, 8: product0_.name as name4_, 9: product0_.price as price4_, 10: ROW_NUMBER() OVER( 11: ORDER BY 12: CURRENT_TIMESTAMP) as __hibernate_sort_row 13: from 14: product product0_) as query 15: WHERE 16: query.__hibernate_sort_row > @p1 17: ORDER BY If, however, you wanted to bring as well the associated order details, you might be tempted to try this: 1: session.Query<Product>().Fetch(x => x.OrderDetails).Take(5).Skip(5).ToList(); Which, in turn, will produce this SQL: 1: SELECT 2: TOP (@p0) product1_4_0_, 3: order1_3_1_, 4: name4_0_, 5: price4_0_, 6: order2_3_1_, 7: product3_3_1_, 8: quantity3_1_, 9: product3_0__, 10: order1_0__ 11: FROM 12: (select 13: product0_.product_id as product1_4_0_, 14: orderdetai1_.order_detail_id as order1_3_1_, 15: product0_.name as name4_0_, 16: product0_.price as price4_0_, 17: orderdetai1_.order_id as order2_3_1_, 18: orderdetai1_.product_id as product3_3_1_, 19: orderdetai1_.quantity as quantity3_1_, 20: orderdetai1_.product_id as product3_0__, 21: orderdetai1_.order_detail_id as order1_0__, 22: ROW_NUMBER() OVER( 23: ORDER BY 24: CURRENT_TIMESTAMP) as __hibernate_sort_row 25: from 26: product product0_ 27: left outer join 28: order_detail orderdetai1_ 29: on product0_.product_id=orderdetai1_.product_id 30: ) as query 31: WHERE 32: query.__hibernate_sort_row > @p1 33: ORDER BY 34: query.__hibernate_sort_row; However, because of the JOIN, what happens is that, if your products have more than one order details, you will get several records – one per order detail – per product, which means that pagination will be broken. There is an workaround, which forces you to write your LINQ query in another way: 1: session.Query<OrderDetail>().Where(x => session.Query<Product>().Select(y => y.ProductId).Take(5).Skip(5).Contains(x.Product.ProductId)).Select(x => x.Product).ToList() Or, using HQL: 1: session.CreateQuery("select od.Product from OrderDetail od where od.Product.ProductId in (select p.ProductId from Product p skip 5 take 5)").List<Product>(); The generated SQL will then be: 1: select 2: product1_.product_id as product1_4_, 3: product1_.name as name4_, 4: product1_.price as price4_ 5: from 6: order_detail orderdetai0_ 7: left outer join 8: product product1_ 9: on orderdetai0_.product_id=product1_.product_id 10: where 11: orderdetai0_.product_id in ( 12: SELECT 13: TOP (@p0) product_id 14: FROM 15: (select 16: product2_.product_id, 17: ROW_NUMBER() OVER( 18: ORDER BY 19: CURRENT_TIMESTAMP) as __hibernate_sort_row 20: from 21: product product2_) as query 22: WHERE 23: query.__hibernate_sort_row > @p1 24: ORDER BY 25: query.__hibernate_sort_row); Which will get you what you want: for 5 products, all of their order details.

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• Dynamic LINQ in an Assembly Near By

  - by Ricardo Peres

  You may recall my post on Dynamic LINQ. I said then that you had to download Microsoft's samples and compile the DynamicQuery project (or just grab my copy), but there's another way. It turns out Microsoft included the Dynamic LINQ classes in the System.Web.Extensions assembly, not the one from ASP.NET 2.0, but the one that was included with ASP.NET 3.5! The only problem is that all types are private: Here's how to use it: Assembly asm = typeof(UpdatePanel).Assembly; Type dynamicExpressionType = asm.GetType("System.Web.Query.Dynamic.DynamicExpression"); MethodInfo parseLambdaMethod = dynamicExpressionType.GetMethods(BindingFlags.Public | BindingFlags.Static).Where(m = (m.Name == "ParseLambda") && (m.GetParameters().Length == 2)).Single().MakeGenericMethod(typeof(DateTime), typeof(Boolean)); Func filterExpression = (parseLambdaMethod.Invoke(null, new Object [] { "Year == 2010", new Object [ 0 ] }) as Expression).Compile(); List list = new List { new DateTime(2010, 1, 1), new DateTime(1999, 1, 12), new DateTime(1900, 10, 10), new DateTime(1900, 2, 20), new DateTime(2012, 5, 5), new DateTime(2012, 1, 20) }; IEnumerable filteredDates = list.Where(filterExpression); SyntaxHighlighter.config.clipboardSwf = 'http://alexgorbatchev.com/pub/sh/2.0.320/scripts/clipboard.swf'; SyntaxHighlighter.brushes.CSharp.aliases = ['c#', 'c-sharp', 'csharp']; SyntaxHighlighter.all();

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• Change Tracking

  - by Ricardo Peres

  You may recall my last post on Change Data Control. This time I am going to talk about other option for tracking changes to tables on SQL Server: Change Tracking. The main differences between the two are: Change Tracking works with SQL Server 2008 Express Change Tracking does not require SQL Server Agent to be running Change Tracking does not keep the old values in case of an UPDATE or DELETE Change Data Capture uses an asynchronous process, so there is no overhead on each operation Change Data Capture requires more storage and processing Here's some code that illustrates it's usage: -- for demonstrative purposes, table Post of database Blog only contains two columns, PostId and Title -- enable change tracking for database Blog, for 2 days ALTER DATABASE Blog SET CHANGE_TRACKING = ON (CHANGE_RETENTION = 2 DAYS, AUTO_CLEANUP = ON); -- enable change tracking for table Post ALTER TABLE Post ENABLE CHANGE_TRACKING WITH (TRACK_COLUMNS_UPDATED = ON); -- see current records on table Post SELECT * FROM Post SELECT * FROM sys.sysobjects WHERE name = 'Post' SELECT * FROM sys.sysdatabases WHERE name = 'Blog' -- confirm that table Post and database Blog are being change tracked SELECT * FROM sys.change_tracking_tables SELECT * FROM sys.change_tracking_databases -- see current version for table Post SELECT p.PostId, p.Title, c.SYS_CHANGE_VERSION, c.SYS_CHANGE_CONTEXT FROM Post AS p CROSS APPLY CHANGETABLE(VERSION Post, (PostId), (p.PostId)) AS c; -- update post UPDATE Post SET Title = 'First Post Title Changed' WHERE Title = 'First Post Title'; -- see current version for table Post SELECT p.PostId, p.Title, c.SYS_CHANGE_VERSION, c.SYS_CHANGE_CONTEXT FROM Post AS p CROSS APPLY CHANGETABLE(VERSION Post, (PostId), (p.PostId)) AS c; -- see changes since version 0 (initial) SELECT p.Title, c.PostId, SYS_CHANGE_VERSION, SYS_CHANGE_OPERATION, SYS_CHANGE_COLUMNS, SYS_CHANGE_CONTEXT FROM CHANGETABLE(CHANGES Post, 0) AS c LEFT OUTER JOIN Post AS p ON p.PostId = c.PostId; -- is column Title of table Post changed since version 0? SELECT CHANGE_TRACKING_IS_COLUMN_IN_MASK(COLUMNPROPERTY(OBJECT_ID('Post'), 'Title', 'ColumnId'), (SELECT SYS_CHANGE_COLUMNS FROM CHANGETABLE(CHANGES Post, 0) AS c)) -- get current version SELECT CHANGE_TRACKING_CURRENT_VERSION() -- disable change tracking for table Post ALTER TABLE Post DISABLE CHANGE_TRACKING; -- disable change tracking for database Blog ALTER DATABASE Blog SET CHANGE_TRACKING = OFF; You can read about the differences between the two options here. Choose the one that best suits your needs! SyntaxHighlighter.config.clipboardSwf = 'http://alexgorbatchev.com/pub/sh/2.0.320/scripts/clipboard.swf'; SyntaxHighlighter.brushes.CSharp.aliases = ['c#', 'c-sharp', 'csharp']; SyntaxHighlighter.brushes.Xml.aliases = ['xml']; SyntaxHighlighter.all();

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• Wrapping ASP.NET Client Callbacks

  - by Ricardo Peres

  Client Callbacks are probably the less known (and I dare say, less loved) of all the AJAX options in ASP.NET, which also include the UpdatePanel, Page Methods and Web Services. The reason for that, I believe, is it’s relative complexity: Get a reference to a JavaScript function; Dynamically register function that calls the above reference; Have a JavaScript handler call the registered function. However, it has some the nice advantage of being self-contained, that is, doesn’t need additional files, such as web services, JavaScript libraries, etc, or static methods declared on a page, or any kind of attributes. So, here’s what I want to do: Have a DOM element which exposes a method that is executed server side, passing it a string and returning a string; Have a server-side event that handles the client-side call; Have two client-side user-supplied callback functions for handling the success and error results. I’m going to develop a custom control without user interface that does the registration of the client JavaScript method as well as a server-side event that can be hooked by some handler on a page. My markup will look like this: 1: <script type="text/javascript"> 1:  2:  3: function onCallbackSuccess(result, context) 4: { 5: } 6:  7: function onCallbackError(error, context) 8: { 9: } 10:  </script> 2: <my:CallbackControl runat="server" ID="callback" SendAllData="true" OnCallback="OnCallback"/> The control itself looks like this: 1: public class CallbackControl : Control, ICallbackEventHandler 2: { 3: #region Public constructor 4: public CallbackControl() 5: { 6: this.SendAllData = false; 7: this.Async = true; 8: } 9: #endregion 10:  11: #region Public properties and events 12: public event EventHandler<CallbackEventArgs> Callback; 13:  14: [DefaultValue(true)] 15: public Boolean Async 16: { 17: get; 18: set; 19: } 20:  21: [DefaultValue(false)] 22: public Boolean SendAllData 23: { 24: get; 25: set; 26: } 27:  28: #endregion 29:  30: #region Protected override methods 31:  32: protected override void Render(HtmlTextWriter writer) 33: { 34: writer.AddAttribute(HtmlTextWriterAttribute.Id, this.ClientID); 35: writer.RenderBeginTag(HtmlTextWriterTag.Span); 36:  37: base.Render(writer); 38:  39: writer.RenderEndTag(); 40: } 41:  42: protected override void OnInit(EventArgs e) 43: { 44: String reference = this.Page.ClientScript.GetCallbackEventReference(this, "arg", "onCallbackSuccess", "context", "onCallbackError", this.Async); 45: String script = String.Concat("\ndocument.getElementById('", this.ClientID, "').callback = function(arg, context, onCallbackSuccess, onCallbackError){", ((this.SendAllData == true) ? "__theFormPostCollection.length = 0; __theFormPostData = ''; WebForm_InitCallback(); " : String.Empty), reference, ";};\n"); 46:  47: this.Page.ClientScript.RegisterStartupScript(this.GetType(), String.Concat("callback", this.ClientID), script, true); 48:  49: base.OnInit(e); 50: } 51:  52: #endregion 53:  54: #region Protected virtual methods 55: protected virtual void OnCallback(CallbackEventArgs args) 56: { 57: EventHandler<CallbackEventArgs> handler = this.Callback; 58:  59: if (handler != null) 60: { 61: handler(this, args); 62: } 63: } 64:  65: #endregion 66:  67: #region ICallbackEventHandler Members 68:  69: String ICallbackEventHandler.GetCallbackResult() 70: { 71: CallbackEventArgs args = new CallbackEventArgs(this.Context.Items["Data"] as String); 72:  73: this.OnCallback(args); 74:  75: return (args.Result); 76: } 77:  78: void ICallbackEventHandler.RaiseCallbackEvent(String eventArgument) 79: { 80: this.Context.Items["Data"] = eventArgument; 81: } 82:  83: #endregion 84: } And the event argument class: 1: [Serializable] 2: public class CallbackEventArgs : EventArgs 3: { 4: public CallbackEventArgs(String argument) 5: { 6: this.Argument = argument; 7: this.Result = String.Empty; 8: } 9:  10: public String Argument 11: { 12: get; 13: private set; 14: } 15:  16: public String Result 17: { 18: get; 19: set; 20: } 21: } You will notice two properties on the CallbackControl: Async: indicates if the call should be made asynchronously or synchronously (the default); SendAllData: indicates if the callback call will include the view and control state of all of the controls on the page, so that, on the server side, they will have their properties set when the Callback event is fired. The CallbackEventArgs class exposes two properties: Argument: the read-only argument passed to the client-side function; Result: the result to return to the client-side callback function, set from the Callback event handler. An example of an handler for the Callback event would be: 1: protected void OnCallback(Object sender, CallbackEventArgs e) 2: { 3: e.Result = String.Join(String.Empty, e.Argument.Reverse()); 4: } Finally, in order to fire the Callback event from the client, you only need this: 1: <input type="text" id="input"/> 2: <input type="button" value="Get Result" onclick="document.getElementById('callback').callback(callback(document.getElementById('input').value, 'context', onCallbackSuccess, onCallbackError))"/> The syntax of the callback function is: arg: some string argument; context: some context that will be passed to the callback functions (success or failure); callbackSuccessFunction: some function that will be called when the callback succeeds; callbackFailureFunction: some function that will be called if the callback fails for some reason. Give it a try and see if it helps!

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• Unity – Part 5: Injecting Values

  - by Ricardo Peres

  Introduction This is the fifth post on Unity. You can find the introductory post here, the second post, on dependency injection here, a third one on Aspect Oriented Programming (AOP) here and the latest so far, on writing custom extensions, here. This time we will talk about injecting simple values. An Inversion of Control (IoC) / Dependency Injector (DI) container like Unity can be used for things other than injecting complex class dependencies. It can also be used for setting property values or method/constructor parameters whenever a class is built. The main difference is that these values do not have a lifetime manager associated with them and do not come from the regular IoC registration store. Unlike, for instance, MEF, Unity won’t let you register as a dependency a string or an integer, so you have to take a different approach, which I will describe in this post. Scenario Let’s imagine we have a base interface that describes a logger – the same as in previous examples: 1: public interface ILogger 2: { 3: void Log(String message); 4: } And a concrete implementation that writes to a file: 1: public class FileLogger : ILogger 2: { 3: public String Filename 4: { 5: get; 6: set; 7: } 8:  9: #region ILogger Members 10:  11: public void Log(String message) 12: { 13: using (Stream file = File.OpenWrite(this.Filename)) 14: { 15: Byte[] data = Encoding.Default.GetBytes(message); 16: 17: file.Write(data, 0, data.Length); 18: } 19: } 20:  21: #endregion 22: } And let’s say we want the Filename property to come from the application settings (appSettings) section on the Web/App.config file. As usual with Unity, there is an extensibility point that allows us to automatically do this, both with code configuration or statically on the configuration file. Extending Injection We start by implementing a class that will retrieve a value from the appSettings by inheriting from ValueElement: 1: sealed class AppSettingsParameterValueElement : ValueElement, IDependencyResolverPolicy 2: { 3: #region Private methods 4: private Object CreateInstance(Type parameterType) 5: { 6: Object configurationValue = ConfigurationManager.AppSettings[this.AppSettingsKey]; 7:  8: if (parameterType != typeof(String)) 9: { 10: TypeConverter typeConverter = this.GetTypeConverter(parameterType); 11:  12: configurationValue = typeConverter.ConvertFromInvariantString(configurationValue as String); 13: } 14:  15: return (configurationValue); 16: } 17: #endregion 18:  19: #region Private methods 20: private TypeConverter GetTypeConverter(Type parameterType) 21: { 22: if (String.IsNullOrEmpty(this.TypeConverterTypeName) == false) 23: { 24: return (Activator.CreateInstance(TypeResolver.ResolveType(this.TypeConverterTypeName)) as TypeConverter); 25: } 26: else 27: { 28: return (TypeDescriptor.GetConverter(parameterType)); 29: } 30: } 31: #endregion 32:  33: #region Public override methods 34: public override InjectionParameterValue GetInjectionParameterValue(IUnityContainer container, Type parameterType) 35: { 36: Object value = this.CreateInstance(parameterType); 37: return (new InjectionParameter(parameterType, value)); 38: } 39: #endregion 40:  41: #region IDependencyResolverPolicy Members 42:  43: public Object Resolve(IBuilderContext context) 44: { 45: Type parameterType = null; 46:  47: if (context.CurrentOperation is ResolvingPropertyValueOperation) 48: { 49: ResolvingPropertyValueOperation op = (context.CurrentOperation as ResolvingPropertyValueOperation); 50: PropertyInfo prop = op.TypeBeingConstructed.GetProperty(op.PropertyName); 51: parameterType = prop.PropertyType; 52: } 53: else if (context.CurrentOperation is ConstructorArgumentResolveOperation) 54: { 55: ConstructorArgumentResolveOperation op = (context.CurrentOperation as ConstructorArgumentResolveOperation); 56: String args = op.ConstructorSignature.Split('(')[1].Split(')')[0]; 57: Type[] types = args.Split(',').Select(a => Type.GetType(a.Split(' ')[0])).ToArray(); 58: ConstructorInfo ctor = op.TypeBeingConstructed.GetConstructor(types); 59: parameterType = ctor.GetParameters().Where(p => p.Name == op.ParameterName).Single().ParameterType; 60: } 61: else if (context.CurrentOperation is MethodArgumentResolveOperation) 62: { 63: MethodArgumentResolveOperation op = (context.CurrentOperation as MethodArgumentResolveOperation); 64: String methodName = op.MethodSignature.Split('(')[0].Split(' ')[1]; 65: String args = op.MethodSignature.Split('(')[1].Split(')')[0]; 66: Type[] types = args.Split(',').Select(a => Type.GetType(a.Split(' ')[0])).ToArray(); 67: MethodInfo method = op.TypeBeingConstructed.GetMethod(methodName, types); 68: parameterType = method.GetParameters().Where(p => p.Name == op.ParameterName).Single().ParameterType; 69: } 70:  71: return (this.CreateInstance(parameterType)); 72: } 73:  74: #endregion 75:  76: #region Public properties 77: [ConfigurationProperty("appSettingsKey", IsRequired = true)] 78: public String AppSettingsKey 79: { 80: get 81: { 82: return ((String)base["appSettingsKey"]); 83: } 84:  85: set 86: { 87: base["appSettingsKey"] = value; 88: } 89: } 90: #endregion 91: } As you can see from the implementation of the IDependencyResolverPolicy.Resolve method, this will work in three different scenarios: When it is applied to a property; When it is applied to a constructor parameter; When it is applied to an initialization method. The implementation will even try to convert the value to its declared destination, for example, if the destination property is an Int32, it will try to convert the appSettings stored string to an Int32. Injection By Configuration If we want to configure injection by configuration, we need to implement a custom section extension by inheriting from SectionExtension, and registering our custom element with the name “appSettings”: 1: sealed class AppSettingsParameterInjectionElementExtension : SectionExtension 2: { 3: public override void AddExtensions(SectionExtensionContext context) 4: { 5: context.AddElement<AppSettingsParameterValueElement>("appSettings"); 6: } 7: } And on the configuration file, for setting a property, we use it like this: 1: <appSettings> 2: <add key="LoggerFilename" value="Log.txt"/> 3: </appSettings> 4: <unity xmlns="http://schemas.microsoft.com/practices/2010/unity"> 5: <container> 6: <register type="MyNamespace.ILogger, MyAssembly" mapTo="MyNamespace.ConsoleLogger, MyAssembly"/> 7: <register type="MyNamespace.ILogger, MyAssembly" mapTo="MyNamespace.FileLogger, MyAssembly" name="File"> 8: <lifetime type="singleton"/> 9: <property name="Filename"> 10: <appSettings appSettingsKey="LoggerFilename"/> 11: </property> 12: </register> 13: </container> 14: </unity> If we would like to inject the value as a constructor parameter, it would be instead: 1: <unity xmlns="http://schemas.microsoft.com/practices/2010/unity"> 2: <sectionExtension type="MyNamespace.AppSettingsParameterInjectionElementExtension, MyAssembly" /> 3: <container> 4: <register type="MyNamespace.ILogger, MyAssembly" mapTo="MyNamespace.ConsoleLogger, MyAssembly"/> 5: <register type="MyNamespace.ILogger, MyAssembly" mapTo="MyNamespace.FileLogger, MyAssembly" name="File"> 6: <lifetime type="singleton"/> 7: <constructor> 8: <param name="filename" type="System.String"> 9: <appSettings appSettingsKey="LoggerFilename"/> 10: </param> 11: </constructor> 12: </register> 13: </container> 14: </unity> Notice the appSettings section, where we add a LoggerFilename entry, which is the same as the one referred by our AppSettingsParameterInjectionElementExtension extension. For more advanced behavior, you can add a TypeConverterName attribute to the appSettings declaration, where you can pass an assembly qualified name of a class that inherits from TypeConverter. This class will be responsible for converting the appSettings value to a destination type. Injection By Attribute If we would like to use attributes instead, we need to create a custom attribute by inheriting from DependencyResolutionAttribute: 1: [Serializable] 2: [AttributeUsage(AttributeTargets.Parameter | AttributeTargets.Property, AllowMultiple = false, Inherited = true)] 3: public sealed class AppSettingsDependencyResolutionAttribute : DependencyResolutionAttribute 4: { 5: public AppSettingsDependencyResolutionAttribute(String appSettingsKey) 6: { 7: this.AppSettingsKey = appSettingsKey; 8: } 9:  10: public String TypeConverterTypeName 11: { 12: get; 13: set; 14: } 15:  16: public String AppSettingsKey 17: { 18: get; 19: private set; 20: } 21:  22: public override IDependencyResolverPolicy CreateResolver(Type typeToResolve) 23: { 24: return (new AppSettingsParameterValueElement() { AppSettingsKey = this.AppSettingsKey, TypeConverterTypeName = this.TypeConverterTypeName }); 25: } 26: } As for file configuration, there is a mandatory property for setting the appSettings key and an optional TypeConverterName  for setting the name of a TypeConverter. Both the custom attribute and the custom section return an instance of the injector AppSettingsParameterValueElement that we implemented in the first place. Now, the attribute needs to be placed before the injected class’ Filename property: 1: public class FileLogger : ILogger 2: { 3: [AppSettingsDependencyResolution("LoggerFilename")] 4: public String Filename 5: { 6: get; 7: set; 8: } 9:  10: #region ILogger Members 11:  12: public void Log(String message) 13: { 14: using (Stream file = File.OpenWrite(this.Filename)) 15: { 16: Byte[] data = Encoding.Default.GetBytes(message); 17: 18: file.Write(data, 0, data.Length); 19: } 20: } 21:  22: #endregion 23: } Or, if we wanted to use constructor injection: 1: public class FileLogger : ILogger 2: { 3: public String Filename 4: { 5: get; 6: set; 7: } 8:  9: public FileLogger([AppSettingsDependencyResolution("LoggerFilename")] String filename) 10: { 11: this.Filename = filename; 12: } 13:  14: #region ILogger Members 15:  16: public void Log(String message) 17: { 18: using (Stream file = File.OpenWrite(this.Filename)) 19: { 20: Byte[] data = Encoding.Default.GetBytes(message); 21: 22: file.Write(data, 0, data.Length); 23: } 24: } 25:  26: #endregion 27: } Usage Just do: 1: ILogger logger = ServiceLocator.Current.GetInstance<ILogger>("File"); And off you go! A simple way do avoid hardcoded values in component registrations. Of course, this same concept can be applied to registry keys, environment values, XML attributes, etc, etc, just change the implementation of the AppSettingsParameterValueElement class. Next stop: custom lifetime managers.

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• ASP.NET MVC CRUD Validation

  - by Ricardo Peres

  One thing I didn’t refer on my previous post on ASP.NET MVC CRUD with AJAX was how to retrieve model validation information into the client. We want to send any model validation errors to the client in the JSON object that contains the ProductId, RowVersion and Success properties, specifically, if there are any errors, we will add an extra Errors collection property. Here’s how: 1: [HttpPost] 2: [AjaxOnly] 3: [Authorize] 4: public JsonResult Edit(Product product) 5: { 6: if (this.ModelState.IsValid == true) 7: { 8: using (ProductContext ctx = new ProductContext()) 9: { 10: Boolean success = false; 11:  12: ctx.Entry(product).State = (product.ProductId == 0) ? EntityState.Added : EntityState.Modified; 13:  14: try 15: { 16: success = (ctx.SaveChanges() == 1); 17: } 18: catch (DbUpdateConcurrencyException) 19: { 20: ctx.Entry(product).Reload(); 21: } 22:  23: return (this.Json(new { Success = success, ProductId = product.ProductId, RowVersion = Convert.ToBase64String(product.RowVersion) })); 24: } 25: } 26: else 27: { 28: Dictionary<String, String> errors = new Dictionary<String, String>(); 29:  30: foreach (KeyValuePair<String, ModelState> keyValue in this.ModelState) 31: { 32: String key = keyValue.Key; 33: ModelState modelState = keyValue.Value; 34:  35: foreach (ModelError error in modelState.Errors) 36: { 37: errors[key] = error.ErrorMessage; 38: } 39: } 40:  41: return (this.Json(new { Success = false, ProductId = 0, RowVersion = String.Empty, Errors = errors })); 42: } 43: } As for the view, we need to change slightly the onSuccess JavaScript handler on the Single view: 1: function onSuccess(ctx) 2: { 3: if (typeof (ctx.Success) != 'undefined') 4: { 5: $('input#ProductId').val(ctx.ProductId); 6: $('input#RowVersion').val(ctx.RowVersion); 7:  8: if (ctx.Success == false) 9: { 10: var errors = ''; 11:  12: if (typeof (ctx.Errors) != 'undefined') 13: { 14: for (var key in ctx.Errors) 15: { 16: errors += key + ': ' + ctx.Errors[key] + '\n'; 17: } 18:  19: window.alert('An error occurred while updating the entity: the model contained the following errors.\n\n' + errors); 20: } 21: else 22: { 23: window.alert('An error occurred while updating the entity: it may have been modified by third parties. Please try again.'); 24: } 25: } 26: else 27: { 28: window.alert('Saved successfully'); 29: } 30: } 31: else 32: { 33: if (window.confirm('Not logged in. Login now?') == true) 34: { 35: document.location.href = '<% 1: : FormsAuthentication.LoginUrl %>?ReturnURL=' + document.location.pathname; 36: } 37: } 38: } The logic is as this: If the Edit action method is called for a new entity (the ProductId is 0) and it is valid, the entity is saved, and the JSON results contains a Success flag set to true, a ProductId property with the database-generated primary key and a RowVersion with the server-generated ROWVERSION; If the model is not valid, the JSON result will contain the Success flag set to false and the Errors collection populated with all the model validation errors; If the entity already exists in the database (ProductId not 0) and the model is valid, but the stored ROWVERSION is different that the one on the view, the result will set the Success property to false and will return the current (as loaded from the database) value of the ROWVERSION on the RowVersion property. On a future post I will talk about the possibilities that exist for performing model validation, stay tuned!

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