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  • Which is the good way to update object in EF6

    - by TrieuH
    I have searched and find 2 way to update object in EF var attachedEntity = _context.EntityClasses.Local.First(t => t.Id == entity.Id); //We have it in the context, need to update. if (attachedEntity != null) { var attachedEntry = _context.Entry(attachedEntity); attachedEntry.CurrentValues.SetValues(entity); } else { ////If it's not found locally, we can attach it by setting state to modified. ////This would result in a SQL update statement for all fields ////when SaveChanges is called. var entry = _context.Entry(entity); entry.State = EntityState.Modified; } _context.SaveChanges(); And other way is seem more easy var entity = _context.EntityClasses.FirstOrDefault(t => t.Id == entity.Id); _context.Entry(entity ).EntityState.Modified _context.SaveChanges(); What is best way to update object? NOTE: the performence is importance with me

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  • Java Basics: create class object

    - by user1767853
    In C++: class Rectangle { int x, y; public: void set_values (int,int); int area () {return (x*y);} }; int main () { Rectangle rect; rect.set_values (3,4); } In Java: class Rectangle { int x, y; void set_values (int x,int y); int area () {return (x*y);} } public static void main(String[] args) { Rectangle rect=new Rectangle(3,4); } In C++ compiler will create rect object & reserve memory 4 bytes. I want to know How Java is creating object?

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  • how to declare object variable name in loop

    - by user3717895
    public class Node{ Node p,l,r; int height; String s; { /** class body**/ } } String[] S=new String[5000]; int i=0; while (i<5000){ Node x=new Node(); x=S[i]; } I want to make 5000 Node object. above code assign same variable name x every time but i want different variable name . then how to declare 5000 class variable name without declaring it manually. is there something by which i can create 5000 Node class object with ease.

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  • NHibernate Conventions

    - by Ricardo Peres
    Introduction It seems that nowadays everyone loves conventions! Not the ones that you go to, but the ones that you use, that is! It just happens that NHibernate also supports conventions, and we’ll see exactly how. Conventions in NHibernate are supported in two ways: Naming of tables and columns when not explicitly indicated in the mappings; Full domain mapping. Naming of Tables and Columns Since always NHibernate has supported the concept of a naming strategy. A naming strategy in NHibernate converts class and property names to table and column names and vice-versa, when a name is not explicitly supplied. In concrete, it must be a realization of the NHibernate.Cfg.INamingStrategy interface, of which NHibernate includes two implementations: DefaultNamingStrategy: the default implementation, where each column and table are mapped to identically named properties and classes, for example, “MyEntity” will translate to “MyEntity”; ImprovedNamingStrategy: underscores (_) are used to separate Pascal-cased fragments, for example, entity “MyEntity” will be mapped to a “my_entity” table. The naming strategy can be defined at configuration level (the Configuration instance) by calling the SetNamingStrategy method: 1: cfg.SetNamingStrategy(ImprovedNamingStrategy.Instance); Both the DefaultNamingStrategy and the ImprovedNamingStrategy classes offer singleton instances in the form of Instance static fields. DefaultNamingStrategy is the one NHibernate uses, if you don’t specify one. Domain Mapping In mapping by code, we have the choice of relying on conventions to do the mapping automatically. This means a class will inspect our classes and decide how they will relate to the database objects. The class that handles conventions is NHibernate.Mapping.ByCode.ConventionModelMapper, a specialization of the base by code mapper, NHibernate.Mapping.ByCode.ModelMapper. The ModelMapper relies on an internal SimpleModelInspector to help it decide what and how to map, but the mapper lets you override its decisions.  You apply code conventions like this: 1: //pick the types that you want to map 2: IEnumerable<Type> types = Assembly.GetExecutingAssembly().GetExportedTypes(); 3:  4: //conventions based mapper 5: ConventionModelMapper mapper = new ConventionModelMapper(); 6:  7: HbmMapping mapping = mapper.CompileMappingFor(types); 8:  9: //the one and only configuration instance 10: Configuration cfg = ...; 11: cfg.AddMapping(mapping); This is a very simple example, it lacks, at least, the id generation strategy, which you can add by adding an event handler like this: 1: mapper.BeforeMapClass += (IModelInspector modelInspector, Type type, IClassAttributesMapper classCustomizer) => 2: { 3: classCustomizer.Id(x => 4: { 5: //set the hilo generator 6: x.Generator(Generators.HighLow); 7: }); 8: }; The mapper will fire events like this whenever it needs to get information about what to do. And basically this is all it takes to automatically map your domain! It will correctly configure many-to-one and one-to-many relations, choosing bags or sets depending on your collections, will get the table and column names from the naming strategy we saw earlier and will apply the usual defaults to all properties, such as laziness and fetch mode. However, there is at least one thing missing: many-to-many relations. The conventional mapper doesn’t know how to find and configure them, which is a pity, but, alas, not difficult to overcome. To start, for my projects, I have this rule: each entity exposes a public property of type ISet<T> where T is, of course, the type of the other endpoint entity. Extensible as it is, NHibernate lets me implement this very easily: 1: mapper.IsOneToMany((MemberInfo member, Boolean isLikely) => 2: { 3: Type sourceType = member.DeclaringType; 4: Type destinationType = member.GetMemberFromDeclaringType().GetPropertyOrFieldType(); 5:  6: //check if the property is of a generic collection type 7: if ((destinationType.IsGenericCollection() == true) && (destinationType.GetGenericArguments().Length == 1)) 8: { 9: Type destinationEntityType = destinationType.GetGenericArguments().Single(); 10:  11: //check if the type of the generic collection property is an entity 12: if (mapper.ModelInspector.IsEntity(destinationEntityType) == true) 13: { 14: //check if there is an equivalent property on the target type that is also a generic collection and points to this entity 15: PropertyInfo collectionInDestinationType = destinationEntityType.GetProperties().Where(x => (x.PropertyType.IsGenericCollection() == true) && (x.PropertyType.GetGenericArguments().Length == 1) && (x.PropertyType.GetGenericArguments().Single() == sourceType)).SingleOrDefault(); 16:  17: if (collectionInDestinationType != null) 18: { 19: return (false); 20: } 21: } 22: } 23:  24: return (true); 25: }); 26:  27: mapper.IsManyToMany((MemberInfo member, Boolean isLikely) => 28: { 29: //a relation is many to many if it isn't one to many 30: Boolean isOneToMany = mapper.ModelInspector.IsOneToMany(member); 31: return (!isOneToMany); 32: }); 33:  34: mapper.BeforeMapManyToMany += (IModelInspector modelInspector, PropertyPath member, IManyToManyMapper collectionRelationManyToManyCustomizer) => 35: { 36: Type destinationEntityType = member.LocalMember.GetPropertyOrFieldType().GetGenericArguments().First(); 37: //set the mapping table column names from each source entity name plus the _Id sufix 38: collectionRelationManyToManyCustomizer.Column(destinationEntityType.Name + "_Id"); 39: }; 40:  41: mapper.BeforeMapSet += (IModelInspector modelInspector, PropertyPath member, ISetPropertiesMapper propertyCustomizer) => 42: { 43: if (modelInspector.IsManyToMany(member.LocalMember) == true) 44: { 45: propertyCustomizer.Key(x => x.Column(member.LocalMember.DeclaringType.Name + "_Id")); 46:  47: Type sourceType = member.LocalMember.DeclaringType; 48: Type destinationType = member.LocalMember.GetPropertyOrFieldType().GetGenericArguments().First(); 49: IEnumerable<String> names = new Type[] { sourceType, destinationType }.Select(x => x.Name).OrderBy(x => x); 50:  51: //set inverse on the relation of the alphabetically first entity name 52: propertyCustomizer.Inverse(sourceType.Name == names.First()); 53: //set mapping table name from the entity names in alphabetical order 54: propertyCustomizer.Table(String.Join("_", names)); 55: } 56: }; We have to understand how the conventions mapper thinks: For each collection of entities found, it will ask the mapper if it is a one-to-many; in our case, if the collection is a generic one that has an entity as its generic parameter, and the generic parameter type has a similar collection, then it is not a one-to-many; Next, the mapper will ask if the collection that it now knows is not a one-to-many is a many-to-many; Before a set is mapped, if it corresponds to a many-to-many, we set its mapping table. Now, this is tricky: because we have no way to maintain state, we sort the names of the two endpoint entities and we combine them with a “_”; for the first alphabetical entity, we set its relation to inverse – remember, on a many-to-many relation, only one endpoint must be marked as inverse; finally, we set the column name as the name of the entity with an “_Id” suffix; Before the many-to-many relation is processed, we set the column name as the name of the other endpoint entity with the “_Id” suffix, as we did for the set. And that’s it. With these rules, NHibernate will now happily find and configure many-to-many relations, as well as all the others. You can wrap this in a new conventions mapper class, so that it is more easily reusable: 1: public class ManyToManyConventionModelMapper : ConventionModelMapper 2: { 3: public ManyToManyConventionModelMapper() 4: { 5: base.IsOneToMany((MemberInfo member, Boolean isLikely) => 6: { 7: return (this.IsOneToMany(member, isLikely)); 8: }); 9:  10: base.IsManyToMany((MemberInfo member, Boolean isLikely) => 11: { 12: return (this.IsManyToMany(member, isLikely)); 13: }); 14:  15: base.BeforeMapManyToMany += this.BeforeMapManyToMany; 16: base.BeforeMapSet += this.BeforeMapSet; 17: } 18:  19: protected virtual Boolean IsManyToMany(MemberInfo member, Boolean isLikely) 20: { 21: //a relation is many to many if it isn't one to many 22: Boolean isOneToMany = this.ModelInspector.IsOneToMany(member); 23: return (!isOneToMany); 24: } 25:  26: protected virtual Boolean IsOneToMany(MemberInfo member, Boolean isLikely) 27: { 28: Type sourceType = member.DeclaringType; 29: Type destinationType = member.GetMemberFromDeclaringType().GetPropertyOrFieldType(); 30:  31: //check if the property is of a generic collection type 32: if ((destinationType.IsGenericCollection() == true) && (destinationType.GetGenericArguments().Length == 1)) 33: { 34: Type destinationEntityType = destinationType.GetGenericArguments().Single(); 35:  36: //check if the type of the generic collection property is an entity 37: if (this.ModelInspector.IsEntity(destinationEntityType) == true) 38: { 39: //check if there is an equivalent property on the target type that is also a generic collection and points to this entity 40: PropertyInfo collectionInDestinationType = destinationEntityType.GetProperties().Where(x => (x.PropertyType.IsGenericCollection() == true) && (x.PropertyType.GetGenericArguments().Length == 1) && (x.PropertyType.GetGenericArguments().Single() == sourceType)).SingleOrDefault(); 41:  42: if (collectionInDestinationType != null) 43: { 44: return (false); 45: } 46: } 47: } 48:  49: return (true); 50: } 51:  52: protected virtual new void BeforeMapManyToMany(IModelInspector modelInspector, PropertyPath member, IManyToManyMapper collectionRelationManyToManyCustomizer) 53: { 54: Type destinationEntityType = member.LocalMember.GetPropertyOrFieldType().GetGenericArguments().First(); 55: //set the mapping table column names from each source entity name plus the _Id sufix 56: collectionRelationManyToManyCustomizer.Column(destinationEntityType.Name + "_Id"); 57: } 58:  59: protected virtual new void BeforeMapSet(IModelInspector modelInspector, PropertyPath member, ISetPropertiesMapper propertyCustomizer) 60: { 61: if (modelInspector.IsManyToMany(member.LocalMember) == true) 62: { 63: propertyCustomizer.Key(x => x.Column(member.LocalMember.DeclaringType.Name + "_Id")); 64:  65: Type sourceType = member.LocalMember.DeclaringType; 66: Type destinationType = member.LocalMember.GetPropertyOrFieldType().GetGenericArguments().First(); 67: IEnumerable<String> names = new Type[] { sourceType, destinationType }.Select(x => x.Name).OrderBy(x => x); 68:  69: //set inverse on the relation of the alphabetically first entity name 70: propertyCustomizer.Inverse(sourceType.Name == names.First()); 71: //set mapping table name from the entity names in alphabetical order 72: propertyCustomizer.Table(String.Join("_", names)); 73: } 74: } 75: } Conclusion Of course, there is much more to mapping than this, I suggest you look at all the events and functions offered by the ModelMapper to see where you can hook for making it behave the way you want. If you need any help, just let me know!

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  • New Enhancements for InnoDB Memcached

    - by Calvin Sun
    In MySQL 5.6, we continued our development on InnoDB Memcached and completed a few widely desirable features that make InnoDB Memcached a competitive feature in more scenario. Notablely, they are 1) Support multiple table mapping 2) Added background thread to auto-commit long running transactions 3) Enhancement in binlog performance  Let’s go over each of these features one by one. And in the last section, we will go over a couple of internally performed performance tests. Support multiple table mapping In our earlier release, all InnoDB Memcached operations are mapped to a single InnoDB table. In the real life, user might want to use this InnoDB Memcached features on different tables. Thus being able to support access to different table at run time, and having different mapping for different connections becomes a very desirable feature. And in this GA release, we allow user just be able to do both. We will discuss the key concepts and key steps in using this feature. 1) "mapping name" in the "get" and "set" command In order to allow InnoDB Memcached map to a new table, the user (DBA) would still require to "pre-register" table(s) in InnoDB Memcached “containers” table (there is security consideration for this requirement). If you would like to know about “containers” table, please refer to my earlier blogs in blogs.innodb.com. Once registered, the InnoDB Memcached will then be able to look for such table when they are referred. Each of such registered table will have a unique "registration name" (or mapping_name) corresponding to the “name” field in the “containers” table.. To access these tables, user will include such "registration name" in their get or set commands, in the form of "get @@new_mapping_name.key", prefix "@@" is required for signaling a mapped table change. The key and the "mapping name" are separated by a configurable delimiter, by default, it is ".". So the syntax is: get [@@mapping_name.]key_name set [@@mapping_name.]key_name  or  get @@mapping_name set @@mapping_name Here is an example: Let's set up three tables in the "containers" table: The first is a map to InnoDB table "test/demo_test" table with mapping name "setup_1" INSERT INTO containers VALUES ("setup_1", "test", "demo_test", "c1", "c2", "c3", "c4", "c5", "PRIMARY");  Similarly, we set up table mappings for table "test/new_demo" with name "setup_2" and that to table "mydatabase/my_demo" with name "setup_3": INSERT INTO containers VALUES ("setup_2", "test", "new_demo", "c1", "c2", "c3", "c4", "c5", "secondary_index_x"); INSERT INTO containers VALUES ("setup_3", "my_database", "my_demo", "c1", "c2", "c3", "c4", "c5", "idx"); To switch to table "my_database/my_demo", and get the value corresponding to “key_a”, user will do: get @@setup_3.key_a (this will also output the value that corresponding to key "key_a" or simply get @@setup_3 Once this is done, this connection will switch to "my_database/my_demo" table until another table mapping switch is requested. so it can continue issue regular command like: get key_b  set key_c 0 0 7 These DMLs will all be directed to "my_database/my_demo" table. And this also implies that different connections can have different bindings (to different table). 2) Delimiter: For the delimiter "." that separates the "mapping name" and key value, we also added a configure option in the "config_options" system table with name of "table_map_delimiter": INSERT INTO config_options VALUES("table_map_delimiter", "."); So if user wants to change to a different delimiter, they can change it in the config_option table. 3) Default mapping: Once we have multiple table mapping, there should be always a "default" map setting. For this, we decided if there exists a mapping name of "default", then this will be chosen as default mapping. Otherwise, the first row of the containers table will chosen as default setting. Please note, user tables can be repeated in the "containers" table (for example, user wants to access different columns of the table in different settings), as long as they are using different mapping/configure names in the first column, which is enforced by a unique index. 4) bind command In addition, we also extend the protocol and added a bind command, its usage is fairly straightforward. To switch to "setup_3" mapping above, you simply issue: bind setup_3 This will switch this connection's InnoDB table to "my_database/my_demo" In summary, with this feature, you now can direct access to difference tables with difference session. And even a single connection, you can query into difference tables. Background thread to auto-commit long running transactions This is a feature related to the “batch” concept we discussed in earlier blogs. This “batch” feature allows us batch the read and write operations, and commit them only after certain calls. The “batch” size is controlled by the configure parameter “daemon_memcached_w_batch_size” and “daemon_memcached_r_batch_size”. This could significantly boost performance. However, it also comes with some disadvantages, for example, you will not be able to view “uncommitted” operations from SQL end unless you set transaction isolation level to read_uncommitted, and in addition, this will held certain row locks for extend period of time that might reduce the concurrency. To deal with this, we introduce a background thread that “auto-commits” the transaction if they are idle for certain amount of time (default is 5 seconds). The background thread will wake up every second and loop through every “connections” opened by Memcached, and check for idle transactions. And if such transaction is idle longer than certain limit and not being used, it will commit such transactions. This limit is configurable by change “innodb_api_bk_commit_interval”. Its default value is 5 seconds, and minimum is 1 second, and maximum is 1073741824 seconds. With the help of such background thread, you will not need to worry about long running uncommitted transactions when set daemon_memcached_w_batch_size and daemon_memcached_r_batch_size to a large number. This also reduces the number of locks that could be held due to long running transactions, and thus further increase the concurrency. Enhancement in binlog performance As you might all know, binlog operation is not done by InnoDB storage engine, rather it is handled in the MySQL layer. In order to support binlog operation through InnoDB Memcached, we would have to artificially create some MySQL constructs in order to access binlog handler APIs. In previous lab release, for simplicity consideration, we open and destroy these MySQL constructs (such as THD) for each operations. This required us to set the “batch” size always to 1 when binlog is on, no matter what “daemon_memcached_w_batch_size” and “daemon_memcached_r_batch_size” are configured to. This put a big restriction on our capability to scale, and also there are quite a bit overhead in creating destroying such constructs that bogs the performance down. With this release, we made necessary change that would keep MySQL constructs as long as they are valid for a particular connection. So there will not be repeated and redundant open and close (table) calls. And now even with binlog option is enabled (with innodb_api_enable_binlog,), we still can batch the transactions with daemon_memcached_w_batch_size and daemon_memcached_r_batch_size, thus scale the write/read performance. Although there are still overheads that makes InnoDB Memcached cannot perform as fast as when binlog is turned off. It is much better off comparing to previous release. And we are continuing optimize the solution is this area to improve the performance as much as possible. Performance Study: Amerandra of our System QA team have conducted some performance studies on queries through our InnoDB Memcached connection and plain SQL end. And it shows some interesting results. The test is conducted on a “Linux 2.6.32-300.7.1.el6uek.x86_64 ix86 (64)” machine with 16 GB Memory, Intel Xeon 2.0 GHz CPU X86_64 2 CPUs- 4 Core Each, 2 RAID DISKS (1027 GB,733.9GB). Results are described in following tables: Table 1: Performance comparison on Set operations Connections 5.6.7-RC-Memcached-plugin ( TPS / Qps) with memcached-threads=8*** 5.6.7-RC* X faster Set (QPS) Set** 8 30,000 5,600 5.36 32 59,000 13,000 4.54 128 68,000 8,000 8.50 512 63,000 6.800 9.23 * mysql-5.6.7-rc-linux2.6-x86_64 ** The “set” operation when implemented in InnoDB Memcached involves a couple of DMLs: it first query the table to see whether the “key” exists, if it does not, the new key/value pair will be inserted. If it does exist, the “value” field of matching row (by key) will be updated. So when used in above query, it is a precompiled store procedure, and query will just execute such procedures. *** added “–daemon_memcached_option=-t8” (default is 4 threads) So we can see with this “set” query, InnoDB Memcached can run 4.5 to 9 time faster than MySQL server. Table 2: Performance comparison on Get operations Connections 5.6.7-RC-Memcached-plugin ( TPS / Qps) with memcached-threads=8 5.6.7-RC* X faster Get (QPS) Get 8 42,000 27,000 1.56 32 101,000 55.000 1.83 128 117,000 52,000 2.25 512 109,000 52,000 2.10 With the “get” query (or the select query), memcached performs 1.5 to 2 times faster than normal SQL. Summary: In summary, we added several much-desired features to InnoDB Memcached in this release, allowing user to operate on different tables with this Memcached interface. We also now provide a background commit thread to commit long running idle transactions, thus allow user to configure large batch write/read without worrying about large number of rows held or not being able to see (uncommit) data. We also greatly enhanced the performance when Binlog is enabled. We will continue making efforts in both performance enhancement and functionality areas to make InnoDB Memcached a good demo case for our InnoDB APIs. Jimmy Yang, September 29, 2012

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  • Banshee crashes consistently - is there a fix?

    - by user36334
    Since updating to ubuntu 11.10 I've had trouble with banshee. In particular when I run it I find that it crashes within an hour without fail. I get the following Unhandled Exception: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.NullReferenceException: Object reference not set to an instance of an object at Mono.Zeroconf.Providers.AvahiDBus.BrowseService.DisposeResolver () [0x00000] in <filename unknown>:0 at Mono.Zeroconf.Providers.AvahiDBus.BrowseService.Dispose () [0x00000] in <filename unknown>:0 at Mono.Zeroconf.Providers.AvahiDBus.ServiceBrowser.OnItemRemove (Int32 interface, Protocol protocol, System.String name, System.String type, System.String domain, LookupResultFlags flags) [0x00000] in <filename unknown>:0 at (wrapper managed-to-native) System.Reflection.MonoMethod:InternalInvoke (System.Reflection.MonoMethod,object,object[],System.Exception&) at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in <filename unknown>:0 --- End of inner exception stack trace --- at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in <filename unknown>:0 at System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) [0x00000] in <filename unknown>:0 at System.Delegate.DynamicInvokeImpl (System.Object[] args) [0x00000] in <filename unknown>:0 at System.MulticastDelegate.DynamicInvokeImpl (System.Object[] args) [0x00000] in <filename unknown>:0 at System.Delegate.DynamicInvoke (System.Object[] args) [0x00000] in <filename unknown>:0 at NDesk.DBus.Connection.HandleSignal (NDesk.DBus.Message msg) [0x00000] in <filename unknown>:0 at NDesk.DBus.Connection.DispatchSignals () [0x00000] in <filename unknown>:0 at NDesk.DBus.Connection.Iterate () [0x00000] in <filename unknown>:0 at Mono.Zeroconf.Providers.AvahiDBus.DBusManager.IterateThread (System.Object o) [0x00000] in <filename unknown>:0 Does anyone else also have this problem?

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  • The dynamic Type in C# Simplifies COM Member Access from Visual FoxPro

    - by Rick Strahl
    I’ve written quite a bit about Visual FoxPro interoperating with .NET in the past both for ASP.NET interacting with Visual FoxPro COM objects as well as Visual FoxPro calling into .NET code via COM Interop. COM Interop with Visual FoxPro has a number of problems but one of them at least got a lot easier with the introduction of dynamic type support in .NET. One of the biggest problems with COM interop has been that it’s been really difficult to pass dynamic objects from FoxPro to .NET and get them properly typed. The only way that any strong typing can occur in .NET for FoxPro components is via COM type library exports of Visual FoxPro components. Due to limitations in Visual FoxPro’s type library support as well as the dynamic nature of the Visual FoxPro language where few things are or can be described in the form of a COM type library, a lot of useful interaction between FoxPro and .NET required the use of messy Reflection code in .NET. Reflection is .NET’s base interface to runtime type discovery and dynamic execution of code without requiring strong typing. In FoxPro terms it’s similar to EVALUATE() functionality albeit with a much more complex API and corresponiding syntax. The Reflection APIs are fairly powerful, but they are rather awkward to use and require a lot of code. Even with the creation of wrapper utility classes for common EVAL() style Reflection functionality dynamically access COM objects passed to .NET often is pretty tedious and ugly. Let’s look at a simple example. In the following code I use some FoxPro code to dynamically create an object in code and then pass this object to .NET. An alternative to this might also be to create a new object on the fly by using SCATTER NAME on a database record. How the object is created is inconsequential, other than the fact that it’s not defined as a COM object – it’s a pure FoxPro object that is passed to .NET. Here’s the code: *** Create .NET COM InstanceloNet = CREATEOBJECT('DotNetCom.DotNetComPublisher') *** Create a Customer Object Instance (factory method) loCustomer = GetCustomer() loCustomer.Name = "Rick Strahl" loCustomer.Company = "West Wind Technologies" loCustomer.creditLimit = 9999999999.99 loCustomer.Address.StreetAddress = "32 Kaiea Place" loCustomer.Address.Phone = "808 579-8342" loCustomer.Address.Email = "[email protected]" *** Pass Fox Object and echo back values ? loNet.PassRecordObject(loObject) RETURN FUNCTION GetCustomer LOCAL loCustomer, loAddress loCustomer = CREATEOBJECT("EMPTY") ADDPROPERTY(loCustomer,"Name","") ADDPROPERTY(loCustomer,"Company","") ADDPROPERTY(loCUstomer,"CreditLimit",0.00) ADDPROPERTY(loCustomer,"Entered",DATETIME()) loAddress = CREATEOBJECT("Empty") ADDPROPERTY(loAddress,"StreetAddress","") ADDPROPERTY(loAddress,"Phone","") ADDPROPERTY(loAddress,"Email","") ADDPROPERTY(loCustomer,"Address",loAddress) RETURN loCustomer ENDFUNC Now prior to .NET 4.0 you’d have to access this object passed to .NET via Reflection and the method code to do this would looks something like this in the .NET component: public string PassRecordObject(object FoxObject) { // *** using raw Reflection string Company = (string) FoxObject.GetType().InvokeMember( "Company", BindingFlags.GetProperty,null, FoxObject,null); // using the easier ComUtils wrappers string Name = (string) ComUtils.GetProperty(FoxObject,"Name"); // Getting Address object – then getting child properties object Address = ComUtils.GetProperty(FoxObject,"Address");    string Street = (string) ComUtils.GetProperty(FoxObject,"StreetAddress"); // using ComUtils 'Ex' functions you can use . Syntax     string StreetAddress = (string) ComUtils.GetPropertyEx(FoxObject,"AddressStreetAddress"); return Name + Environment.NewLine + Company + Environment.NewLine + StreetAddress + Environment.NewLine + " FOX"; } Note that the FoxObject is passed in as type object which has no specific type. Since the object doesn’t exist in .NET as a type signature the object is passed without any specific type information as plain non-descript object. To retrieve a property the Reflection APIs like Type.InvokeMember or Type.GetProperty().GetValue() etc. need to be used. I made this code a little simpler by using the Reflection Wrappers I mentioned earlier but even with those ComUtils calls the code is pretty ugly requiring passing the objects for each call and casting each element. Using .NET 4.0 Dynamic Typing makes this Code a lot cleaner Enter .NET 4.0 and the dynamic type. Replacing the input parameter to the .NET method from type object to dynamic makes the code to access the FoxPro component inside of .NET much more natural: public string PassRecordObjectDynamic(dynamic FoxObject) { // *** using raw Reflection string Company = FoxObject.Company; // *** using the easier ComUtils class string Name = FoxObject.Name; // *** using ComUtils 'ex' functions to use . Syntax string Address = FoxObject.Address.StreetAddress; return Name + Environment.NewLine + Company + Environment.NewLine + Address + Environment.NewLine + " FOX"; } As you can see the parameter is of type dynamic which as the name implies performs Reflection lookups and evaluation on the fly so all the Reflection code in the last example goes away. The code can use regular object ‘.’ syntax to reference each of the members of the object. You can access properties and call methods this way using natural object language. Also note that all the type casts that were required in the Reflection code go away – dynamic types like var can infer the type to cast to based on the target assignment. As long as the type can be inferred by the compiler at compile time (ie. the left side of the expression is strongly typed) no explicit casts are required. Note that although you get to use plain object syntax in the code above you don’t get Intellisense in Visual Studio because the type is dynamic and thus has no hard type definition in .NET . The above example calls a .NET Component from VFP, but it also works the other way around. Another frequent scenario is an .NET code calling into a FoxPro COM object that returns a dynamic result. Assume you have a FoxPro COM object returns a FoxPro Cursor Record as an object: DEFINE CLASS FoxData AS SESSION OlePublic cAppStartPath = "" FUNCTION INIT THIS.cAppStartPath = ADDBS( JustPath(Application.ServerName) ) SET PATH TO ( THIS.cAppStartpath ) ENDFUNC FUNCTION GetRecord(lnPk) LOCAL loCustomer SELECT * FROM tt_Cust WHERE pk = lnPk ; INTO CURSOR TCustomer IF _TALLY < 1 RETURN NULL ENDIF SCATTER NAME loCustomer MEMO RETURN loCustomer ENDFUNC ENDDEFINE If you call this from a .NET application you can now retrieve this data via COM Interop and cast the result as dynamic to simplify the data access of the dynamic FoxPro type that was created on the fly: int pk = 0; int.TryParse(Request.QueryString["id"],out pk); // Create Fox COM Object with Com Callable Wrapper FoxData foxData = new FoxData(); dynamic foxRecord = foxData.GetRecord(pk); string company = foxRecord.Company; DateTime entered = foxRecord.Entered; This code looks simple and natural as it should be – heck you could write code like this in days long gone by in scripting languages like ASP classic for example. Compared to the Reflection code that previously was necessary to run similar code this is much easier to write, understand and maintain. For COM interop and Visual FoxPro operation dynamic type support in .NET 4.0 is a huge improvement and certainly makes it much easier to deal with FoxPro code that calls into .NET. Regardless of whether you’re using COM for calling Visual FoxPro objects from .NET (ASP.NET calling a COM component and getting a dynamic result returned) or whether FoxPro code is calling into a .NET COM component from a FoxPro desktop application. At one point or another FoxPro likely ends up passing complex dynamic data to .NET and for this the dynamic typing makes coding much cleaner and more readable without having to create custom Reflection wrappers. As a bonus the dynamic runtime that underlies the dynamic type is fairly efficient in terms of making Reflection calls especially if members are repeatedly accessed. © Rick Strahl, West Wind Technologies, 2005-2010Posted in COM  FoxPro  .NET  CSharp  

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  • C# Design How to Elegantly wrap a DAL class

    - by guazz
    I have an application which uses MyGeneration's dOODads ORM to generate it's Data Access Layer. dOODad works by generating a persistance class for each table in the database. It works like so: // Load and Save Employees emps = new Employees(); if(emps.LoadByPrimaryKey(42)) { emps.LastName = "Just Got Married"; emps.Save(); } // Add a new record Employees emps = new Employees(); emps.AddNew(); emps.FirstName = "Mr."; emps.LastName = "dOOdad"; emps.Save(); // After save the identity column is already here for me. int i = emps.EmployeeID; // Dynamic Query - All Employees with 'A' in thier last name Employees emps = new Employees(); emps.Where.LastName.Value = "%A%"; emps.Where.LastName.Operator = WhereParameter.Operand.Like; emps.Query.Load(); For the above example(i.e. Employees DAL object) I would like to know what is the best method/technique to abstract some of the implementation details on my classes. I don't believe that an Employee class should have Employees(the DAL) specifics in its methods - or perhaps this is acceptable? Is it possible to implement some form of repository pattern? Bear in mind that this is a high volume, perfomacne critical application. Thanks, j

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  • AntFarm anti-pattern -- strategies to avoid, antidotes to help heal from

    - by alchemical
    I'm working on a 10 page web site with a database back-end. There are 500+ objects in use, trying to implement the MVP pattern in ASP.Net. I'm tracing the code-execution from a single-page, my finger has been on F-11 in Visual Studio for about 40 minutes, there seems to be no end, possibly 1000+ method calls for one web page! If it was just 50 objects that would be one thing, however, code execution snakes through all these objects just like millions of ants frantically woring in their giant dirt mound house, riddled with object tunnels. Hence, a new anti-pattern is born : AntFarm. AntFarm is also known as "OO-Madnes", "OO-Fever", OO-ADD, or simply design-pattern junkie. This is not the first time I've seen this, nor my associates at other companies. It seems that this style is being actively propogated, or in any case is a misunderstanding of the numerous OO/DP gospels going around... I'd like to introduce an anti-pattern to the anti-pattern: GST or "Get Stuff Done" AKA "Get Sh** done" AKA GRD (GetRDone). This pattern focused on just what it says, getting stuff done, in a simple way. I may try to outline it more in a later post, or please share your ideas on this antidote pattern. Anyway, I'm in the midst of a great example of AntFarm anti-pattern as I write (as a bonus, there is no documentation or comments). Please share you thoughts on how this anti-pattern has become so prevelant, how we can avoid it, and how can one undo or deal with this pattern in a live system one must work with!

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  • Classes, methods, and polymorphism in Python

    - by Morlock
    I made a module prototype for building complex timer schedules in python. The classe prototypes permit to have Timer objects, each with their waiting times, Repeat objects that group Timer and other Repeat objects, and a Schedule class, just for holding a whole construction or Timers and Repeat instances. The construction can be as complex as needed and needs to be flexible. Each of these three classes has a .run() method, permitting to go through the whole schedule. Whatever the Class, the .run() method either runs a timer, a repeat group for a certain number of iterations, or a schedule. Is this polymorphism-oriented approach sound or silly? What are other appropriate approaches I should consider to build such a versatile utility that permits to put all building blocks together in as complex a way as desired with simplicity? Thanks! Here is the module code: ##################### ## Importing modules from time import time, sleep ##################### ## Class definitions class Timer: """ Timer object with duration. """ def __init__(self, duration): self.duration = duration def run(self): print "Waiting for %i seconds" % self.duration wait(self.duration) chime() class Repeat: """ Repeat grouped objects for a certain number of repetitions. """ def __init__(self, objects=[], rep=1): self.rep = rep self.objects = objects def run(self): print "Repeating group for %i times" % self.rep for i in xrange(self.rep): for group in self.objects: group.run() class Schedule: """ Groups of timers and repetitions. Maybe redundant with class Repeat. """ def __init__(self, schedule=[]): self.schedule = schedule def run(self): for group in self.schedule: group.run() ######################## ## Function definitions def wait(duration): """ Wait a certain number of seconds. """ time_end = time() + float(duration) #uncoment for minutes# * 60 time_diff = time_end - time() while time_diff > 0: sleep(1) time_diff = time_end - time() def chime(): print "Ding!"

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  • Run unittest in a Class

    - by chrissygormley
    Hello, I have a test suite to perform smoke tests. I have all my script stored in various classes but when I try and run the test suite I can't seem to get it working if it is in a class. The code is below: (a class to call the tests) from alltests import SmokeTests class CallTests(SmokeTests): def integration(self): self.suite() if __name__ == '__main__': run = CallTests() run.integration() And the test suite: class SmokeTests(): def suite(self): #Function stores all the modules to be tested modules_to_test = ('external_sanity', 'internal_sanity') alltests = unittest.TestSuite() for module in map(__import__, modules_to_test): alltests.addTest(unittest.findTestCases(module)) return alltests if __name__ == '__main__': unittest.main(defaultTest='suite') So I can see how to call a normal function defined but I'm finding it difficult calling in the suite. In one of the tests the suite is set up like so: class InternalSanityTestSuite(unittest.TestSuite): # Tests to be tested by test suite def makeInternalSanityTestSuite(): suite = unittest.TestSuite() suite.addTest(TestInternalSanity("BasicInternalSanity")) suite.addTest(TestInternalSanity("VerifyInternalSanityTestFail")) return suite def suite(): return unittest.makeSuite(TestInternalSanity) If I have def suite() inside the class SmokeTests the script executes but the tests don't run but if I remove the class the tests run. I run this as a script and call in variables into the tests. I do not want to have to run the tests by os.system('python tests.py'). I was hoping to call the tests through the class I have like any other function. This need's to be called from a class as the script that I'm calling it from is Object Oriented. If anyone can get the code to be run using Call Tests I would appreciate it alot. Thanks for any help in advance.

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  • Call bindings for DependencyObject when DependencyProperites are changed

    - by melculetz
    Is there a way to notify a DependencyObject's bindinigs when the inner DependencyProperties have changed? For example, I have this class: public class BackgroundDef : DependencyObject { public static readonly DependencyProperty Color1Property = DependencyProperty.Register("Color1", typeof(Color), typeof(Background), new UIPropertyMetadata(Colors.White)); public static readonly DependencyProperty UseBothColorsProperty = DependencyProperty.Register("UseBothColors", typeof(bool), typeof(Background), new UIPropertyMetadata(false)); public static readonly DependencyProperty Color2Property = DependencyProperty.Register("Color2", typeof(Color), typeof(Background), new UIPropertyMetadata(Colors.White)); public Color Color1 { set { SetValue(Color1Property, value); } get { return (Color)GetValue(Color1Property); } } public bool UseBothColors { set { SetValue(UseBothColorsProperty, value); } get { return (bool)GetValue(UseBothColorsProperty); } } public Color Color2 { set { SetValue(Color2Property, value); } get { return (Color)GetValue(Color2Property); } } } For which I have 3 separate two-way bindings that set the values for Color1, Color2 and UseBothColors. But I also have a binding for a BackgroundDef instance, which should create a Brush and draw the background of a button (either a single color, or two gradient colors). My problem is that the two-way bindings for the DependencyProperties update the properties, but the binding for the class instance is not called, as apparently the entire object does not change. Any idea how I could call the bindings for the DependencyObject when the DependencyProperties are changed?

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  • Should business objects be able to create their own DTOs?

    - by Sam
    Suppose I have the following class: class Camera { public Camera( double exposure, double brightness, double contrast, RegionOfInterest regionOfInterest) { this.exposure = exposure; this.brightness = brightness; this.contrast = contrast; this.regionOfInterest = regionOfInterest; } public void ConfigureAcquisitionFifo(IAcquisitionFifo acquisitionFifo) { // do stuff to the acquisition FIFO } readonly double exposure; readonly double brightness; readonly double contrast; readonly RegionOfInterest regionOfInterest; } ... and a DTO to transport the camera info across a service boundary (WCF), say, for viewing in a WinForms/WPF/Web app: using System.Runtime.Serialization; [DataContract] public class CameraData { [DataMember] public double Exposure { get; set; } [DataMember] public double Brightness { get; set; } [DataMember] public double Contrast { get; set; } [DataMember] public RegionOfInterestData RegionOfInterest { get; set; } } Now I can add a method to Camera to expose its data: class Camera { // blah blah public CameraData ToData() { var regionOfInterestData = regionOfInterest.ToData(); return new CameraData() { Exposure = exposure, Brightness = brightness, Contrast = contrast, RegionOfInterestData = regionOfInterestData }; } } or, I can create a method that requires a special IReporter to be passed in for the Camera to expose its data to. This removes the dependency on the Contracts layer (Camera no longer has to know about CameraData): class Camera { // beep beep I'm a jeep public void ExposeToReporter(IReporter reporter) { reporter.GetCameraInfo(exposure, brightness, contrast, regionOfInterest); } } So which should I do? I prefer the second, but it requires the IReporter to have a CameraData field (which gets changed by GetCameraInfo()), which feels weird. Also, if there is any even better solution, please share with me! I'm still an object-oriented newb.

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  • Aren't Information Expert / Tell Don't Ask at odds with Single Responsibility Principle?

    - by moffdub
    It is probably just me, which is why I'm asking the question. Information Expert, Tell Don't Ask, and SRP are often mentioned together as best practices. But I think they are at odds. Here is what I'm talking about: Code that favors SRP but violates Tell Don't Ask, Info Expert: Customer bob = ...; // TransferObjectFactory has to use Customer's accessors to do its work, // violates Tell Don't Ask CustomerDTO dto = TransferObjectFactory.createFrom(bob); Code that favors Tell Don't Ask / Info Expert but violates SRP: Customer bob = ...; // Now Customer is doing more than just representing the domain concept of Customer, // violates SRP CustomerDTO dto = bob.toDTO(); If they are indeed at odds, that's a vindication of my OCD. Otherwise, please fill me in on how these practices can co-exist peacefully. Thank you. Edit: someone wants a definition of the terms - Information Expert: objects that have the data needed for the operation should host the operation Tell Don't Ask: don't ask objects for data in order to do work; tell the objects to do the work Single Responsibility Principle: each object should have a narrowly defined responsibility

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  • MVC design question for forms

    - by kenny99
    Hi, I'm developing an app which has a large amount of related form data to be handled. I'm using a MVC structure and all of the related data is represented in my models, along with the handling of data validation from form submissions. I'm looking for some advice on a good way to approach laying out my controllers - basically I will have a huge form which will be broken down into manageable categories (similar to a credit card app) where the user progresses through each stage/category filling out the answers. All of these form categories are related to the main relation/object, but not to each other. Does it make more sense to have each subform/category as a method in the main controller class (which will make that one controller fairly massive), or would it be better to break each category into a subclass of the main controller? It may be just for neatness that the second approach is better, but I'm struggling to see much of a difference between either creating a new method for each category (which communicates with the model and outputs errors/success) or creating a new controller to handle the same functionality. Thanks in advance for any guidance!

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  • Handling incremental Data Modeling Changes in Functional Programming

    - by Adam Gent
    Most of the problems I have to solve in my job as a developer have to do with data modeling. For example in a OOP Web Application world I often have to change the data properties that are in a object to meet new requirements. If I'm lucky I don't even need to programmatically add new "behavior" code (functions,methods). Instead I can declarative add validation and even UI options by annotating the property (Java). In Functional Programming it seems that adding new data properties requires lots of code changes because of pattern matching and data constructors (Haskell, ML). How do I minimize this problem? This seems to be a recognized problem as Xavier Leroy states nicely on page 24 of "Objects and Classes vs. Modules" - To summarize for those that don't have a PostScript viewer it basically says FP languages are better than OOP languages for adding new behavior over data objects but OOP languages are better for adding new data objects/properties. Are there any design pattern used in FP languages to help mitigate this problem? I have read Phillip Wadler's recommendation of using Monads to help this modularity problem but I'm not sure I understand how?

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  • Spaceship objects

    - by Jam
    I'm trying to make a program which creates a spaceship and I'm using the status() method to display the ship's name and fuel values. However, it doesn't seem to be working. I think I may have messed something up with the status() method. I'm also trying to make it so that I can change the fuel values, but I don't want to create a new method to do so. I think I've taken a horrible wrong turn somewhere in there. Help please! class Ship(object): def __init__(self, name="Enterprise", fuel=0): self.name=name self.fuel=fuel print "The spaceship", name, "has arrived!" def status(): print "Name: ", self.name print "Fuel level: ", self.fuel status=staticmethod(status) def main(): ship1=Ship(raw_input("What would you like to name this ship?")) fuel_level=raw_input("How much fuel does this ship have?") if fuel_level<0: self.fuel=0 else: self.fuel(fuel_level) ship2=Ship(raw_input("What would you like to name this ship?")) fuel_level2=raw_input("How much fuel does this ship have?") if fuel_level2<0: self.fuel=0 else: self.fuel(fuel_level2) ship3=Ship(raw_input("What would you like to name this ship?")) fuel_level3=raw_input("How much fuel does this ship have?") if fuel_level3<0: self.fuel=0 else: self.fuel(fuel_level3) Ship.status() main() raw_input("Press enter to exit.")

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  • iPhone OS: Why is my managedModelObject not complying with Key Value Coding?

    - by nickthedude
    Ok so I'm trying to build this stat tracker for my app and I have built a data model object called statTracker that keeps track of all the stuff I want it to. I can set and retrieve values using the selectors, but if I try and use KVC (ie setValue: forKey: ) everything goes bad and says my StatTracker class is not KVC compliant: valueForUndefinedKey:]: the entity StatTracker is not key value coding-compliant for the key "timesLauched".' 2010-05-18 15:55:08.573 here's the code that is triggering it: NSArray *statTrackerArray = [[NSArray alloc] init]; statTrackerArray = [[CoreDataSingleton sharedCoreDataSingleton] getStatTracker]; NSNumber *number1 = [[NSNumber alloc] init]; number1 = [NSNumber numberWithInt:(1 + [[(StatTracker *)[statTrackerArray objectAtIndex:0] valueForKey:@"timesLauched"] intValue])]; [(StatTracker *)[statTrackerArray objectAtIndex:0] setValue:number1 forKey:@"timesLaunched" ]; NSError *error; if (![[[CoreDataSingleton sharedCoreDataSingleton] managedObjectContext] save:&error]) { NSLog(@"error writing to db"); } Not sure if this is enough code for you folks let me know what you need if you do need more. This would be so sweet if I could use KVC because I could then abstract all this stat tracking stuff into a single method call with a string argument for the value in question. At least that is what I hope to accomplish here. I'm actually now understanding the power of KVC but now I'm just trying to figure out how to make it work. Thanks! Nick

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  • Poor DB4O performance - What am I doing wrong?

    - by Jon
    I read Rob Conery's post about Object databases and thought I'd give it a go. I have a class lets say Book with 15 properties mostly string, some int, one Datetime and 2 decimals. I used Rob's code to open the database file etc to test on a Winforms project not a Web project. So I did the following: for(int i = 0; i < 1000000; i++) { var Book = new Book(); //Assign variables s.Save(Book); } s.CommitChanges(); This took at least a couple of minutes. I then tried to retrieve all data to test speed: var spp = s.All<Passports>(); This one line was quick, however, then doing: sppp.Count() as well as a seperate test doing a foreach loop and incrementing a counter took a couple of minutes. This seems quite slow to me. Am I doing something wrong or am I expecting too much?

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  • function objects versus function pointers

    - by kumar_m_kiran
    Hi All, I have two questions related to function objects and function pointers, Question : 1 When I read the different uses sort algorithm of STL, I see that the third parameter can be a function objects, below is an example class State { public: //... int population() const; float aveTempF() const; //... }; struct PopLess : public std::binary_function<State,State,bool> { bool operator ()( const State &a, const State &b ) const { return popLess( a, b ); } }; sort( union, union+50, PopLess() ); Question : Now, How does the statement, sort(union, union+50,PopLess()) work? PopLess() must be resolved into something like PopLess tempObject.operator() which would be same as executing the operator () function on a temporary object. I see this as, passing the return value of overloaded operation i.e bool (as in my example) to sort algorithm. So then, How does sort function resolve the third parameter in this case? Question : 2 Question Do we derive any particular advantage of using function objects versus function pointer? If we use below function pointer will it derive any disavantage? inline bool popLess( const State &a, const State &b ) { return a.population() < b.population(); } std::sort( union, union+50, popLess ); // sort by population PS : Both the above references(including example) are from book "C++ Common Knowledge: Essential Intermediate Programming" by "Stephen C. Dewhurst". I was unable to decode the topic content, thus have posted for help. Thanks in advance for your help.

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  • How do I create efficient instance variable mutators in Matlab?

    - by Trent B
    Previously, I implemented mutators as follows, however it ran spectacularly slowly on a recursive OO algorithm I'm working on, and I suspected it may have been because I was duplicating objects on every function call... is this correct? %% Example Only obj2 = tripleAllPoints(obj1) obj.pts = obj.pts * 3; obj2 = obj1 end I then tried implementing mutators without using the output object... however, it appears that in MATLAB i can't do this - the changes won't "stick" because of a scope issue? %% Example Only tripleAllPoints(obj1) obj1.pts = obj1.pts * 3; end For application purposes, an extremely simplified version of my code (which uses OO and recursion) is below. classdef myslice properties pts % array of pts nROW % number of rows nDIM % number of dimensions subs % sub-slices end % end properties methods function calcSubs(obj) obj.subs = cell(1,obj.nROW); for i=1:obj.nROW obj.subs{i} = myslice; obj.subs{i}.pts = obj.pts(1:i,2:end); end end function vol = calcVol(obj) if obj.nROW == 1 obj.volume = prod(obj.pts); else obj.volume = 0; calcSubs(obj); for i=1:obj.nROW obj.volume = obj.volume + calcVol(obj.subs{i}); end end end end % end methods end % end classdef

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  • wrapping user controls in a transaction

    - by Hans Gruber
    I'm working on heavily dynamic and configurable CMS system. Therefore, many pages are composed of a dynamically loaded set of user controls. To enable loose coupling between containers (pages) and children (user controls), all user controls are responsible for their own persistence. Each User Control is wired up to its data/service layer dependencies via IoC. They also implement an IPersistable interface, which allows the container .aspx page to issue a Save command to its children without knowledge of the number or exact nature of these user controls. Note: what follows is only pseudo-code: public class MyUserControl : IPersistable, IValidatable { public void Save() { throw new NotImplementedException(); } public bool IsValid() { throw new NotImplementedException(); } } public partial class MyPage { public void btnSave_Click(object sender, EventArgs e) { foreach (IValidatable control in Controls) { if (!control.IsValid) { throw new Exception("error"); } } foreach (IPersistable control in Controls) { if (!control.Save) { throw new Exception("error"); } } } } I'm thinking of using declarative transactions from the System.EnterpriseService namespace to wrap the btnSave_Click in a transaction in case of an exception, but I'm not sure how this might be achieved or any pitfalls to such an approach.

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  • Avoid loading unnecessary data from db into objects (web pages)

    - by GmGr
    Really newbie question coming up. Is there a standard (or good) way to deal with not needing all of the information that a database table contains loaded into every associated object. I'm thinking in the context of web pages where you're only going to use the objects to build a single page rather than an application with longer lived objects. For example, lets say you have an Article table containing id, title, author, date, summary and fullContents fields. You don't need the fullContents to be loaded into the associated objects if you're just showing a page containing a list of articles with their summaries. On the other hand if you're displaying a specific article you might want every field loaded for that one article and maybe just the titles for the other articles (e.g. for display in a recent articles sidebar). Some techniques I can think of: Don't worry about it, just load everything from the database every time. Have several different, possibly inherited, classes for each table and create the appropriate one for the situation (e.g. SummaryArticle, FullArticle). Use one class but set unused properties to null at creation if that field is not needed and be careful. Give the objects access to the database so they can load some fields on demand. Something else? All of the above seem to have fairly major disadvantages. I'm fairly new to programming, very new to OOP and totally new to databases so I might be completely missing the obvious answer here. :)

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  • JAXB Web Services: Multiple Object Marshalling

    - by Luke Evans
    I can marshal and unmarshal 1 object with no problems (in netbeans); I need to know how to do this with multiple objects? I can't generate anything but null pointer exceptions when trying to unmarshal 3 objects into an array from XML; so I don't even know if I've marshalled the 3 out correctly. I know the basic idea of declaring the object, then using the jaxbu or jaxbm command, but I'd like to see this working for more than one object. **TLDR: How do I marshal/unmarshal multiple objects of a single class into/out of XML?? THANKS Code I have that marshals one object from XML: try { JAXBContext jc = JAXBContext.newInstance ("myOffers"); Unmarshaller u = jc.createUnmarshaller (); myOffers.Offer flight = (myOffers.Offer) u.unmarshal( new FileInputStream( "offers.xml" )); System.out.println ("Airline is : " + flight.getAirline()); System.out.println ("Origin is : " + flight.getOrigin()); System.out.println ("Destination is : " + flight.getDestination()); System.out.println ("Seats available : " + flight.getSeats()); System.out.println("Proximity to City Centre is : " + flight.getProximity()); System.out.println("Currency : " + flight.fare.getCurrency()); System.out.println("Value : " + flight.fare.getValue()); } catch (JAXBException e) { System.out.println("Error " + e);} ok so the Xml is: <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <ns2:offer xmlns:ns2="http://simple.example.com/CInfoXmlDoc"> <Origin>Nottingham</Origin> <Destination>Istanbul</Destination> <Airline>Lufthansa</Airline> <Proximity>10</Proximity> <Seats>260</Seats> <Fare> <Currency>GBP</Currency> <Value>300</Value> </Fare> </ns2:offer> <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <ns2:offer xmlns:ns2="http://simple.example.com/CInfoXmlDoc"> <Origin>Birmingham</Origin> <Destination>Cairo</Destination> <Airline>Monarch</Airline> <Proximity>15</Proximity> <Seats>350</Seats> <Fare> <Currency>GBP</Currency> <Value>300</Value> </Fare> </ns2:offer> public static void main(String[] args) throws FileNotFoundException { int i = 0; int arraySize = 2; myOffers.Offer offer[] = new myOffers.Offer[arraySize]; offer[i] = new myOffers.Offer(); offer[i].fare = new myOffers.Offer.Fare(); offer[i].setAirline("Lufthansa"); offer[i].setOrigin("Nottingham"); offer[i].setDestination("Istanbul"); offer[i].setSeats(260); offer[i].setProximity(10); offer[i].fare.currency = "GBP"; offer[i].fare.value = 300; i++; offer[i] = new myOffers.Offer(); offer[i].fare = new myOffers.Offer.Fare(); offer[i].setAirline("Monarch"); offer[i].setOrigin("Birmingham"); offer[i].setDestination("Cairo"); offer[i].setSeats(350); offer[i].setProximity(15); offer[i].fare.currency = "GBP"; offer[i].fare.value = 300; try { int n = 0; FileOutputStream f = new FileOutputStream("offers.xml"); javax.xml.bind.JAXBContext jaxbCtx = javax.xml.bind.JAXBContext.newInstance(offer[n].getClass().getPackage().getName()); javax.xml.bind.Marshaller marshaller = jaxbCtx.createMarshaller(); marshaller.setProperty(javax.xml.bind.Marshaller.JAXB_ENCODING, "UTF-8"); //NOI18N marshaller.setProperty(javax.xml.bind.Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE); while (n < arraySize) { marshaller.marshal(offer[n], f); n++; } } catch (javax.xml.bind.JAXBException ex) { // XXXTODO Handle exception java.util.logging.Logger.getLogger("global").log(java.util.logging.Level.SEVERE, null, ex); //NOI18N } } Which was generated by my marshal code found here: public static void main(String[] args) throws FileNotFoundException { int i = 0; int arraySize = 2; myOffers.Offer offer[] = new myOffers.Offer[arraySize]; offer[i] = new myOffers.Offer(); offer[i].fare = new myOffers.Offer.Fare(); offer[i].setAirline("Lufthansa"); offer[i].setOrigin("Nottingham"); offer[i].setDestination("Istanbul"); offer[i].setSeats(260); offer[i].setProximity(10); offer[i].fare.currency = "GBP"; offer[i].fare.value = 300; i++; offer[i] = new myOffers.Offer(); offer[i].fare = new myOffers.Offer.Fare(); offer[i].setAirline("Monarch"); offer[i].setOrigin("Birmingham"); offer[i].setDestination("Cairo"); offer[i].setSeats(350); offer[i].setProximity(15); offer[i].fare.currency = "GBP"; offer[i].fare.value = 300; try { int n = 0; FileOutputStream f = new FileOutputStream("offers.xml"); javax.xml.bind.JAXBContext jaxbCtx = javax.xml.bind.JAXBContext.newInstance(offer[n].getClass().getPackage().getName()); javax.xml.bind.Marshaller marshaller = jaxbCtx.createMarshaller(); marshaller.setProperty(javax.xml.bind.Marshaller.JAXB_ENCODING, "UTF-8"); //NOI18N marshaller.setProperty(javax.xml.bind.Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE); while (n < arraySize) { marshaller.marshal(offer[n], f); n++; } } catch (javax.xml.bind.JAXBException ex) { // XXXTODO Handle exception java.util.logging.Logger.getLogger("global").log(java.util.logging.Level.SEVERE, null, ex); //NOI18N } } Apologies, I'm fining this editor quite appalling but thats another matter. Whats wrong with [code][/code] tags...

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