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  • How to map inheritance with property returned other inheritance?

    - by dario-g
    Hi I have abstract class Vehicle and two classes that derive from: Car and ForkLift. public abstract class Vehicle { public EngineBase Engine { get; set; } } public class Car : Vehicle { public GasEngine Engine { get; set; } } public class ForkLift : Vehicle { public ElectricEngine Engine { get; set; } } and Engine clasess: public abstract class Engine { } public class GasEngine : Engine { } public class ElectricEngine : Engine { } Engines are mapped with "table per class hierarchy". With Vehicles I want to use the same pattern. How to map Engine class and derived with that Engine property?

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  • How can I map URLs to filenames with perl?

    - by eugene y
    In a simple webapp I need to map URLs to filenames or filepaths. This app has a requirement that it can depend only on modules in the core Perl ditribution (5.6.0 and later). The problem is that filename length on most filesystems is limited to 255. Another limit is about 32k subdirectories in a single folder. My solution: my $filename = $url; if (length($filename) > $MAXPATHLEN) { # if filename longer than 255 my $part1 = substr($filename, 0, $MAXPATHLEN - 13); # first 242 chars my $part2 = crypt(0, substr($filename, $MAXPATHLEN - 13)); # 13 chars hash $filename = $part1.$part2; } $filename =~ s!/!_!g; # escape directory separator Is it reliable ? How can it be improved ?

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  • How would I use for_each to delete every value in an STL map?

    - by stusmith
    Suppose I have a STL map where the values are pointers, and I want to delete them all. How would I represent the following code, but making use of std::for_each? I'm happy for solutions to use Boost. for( stdext::hash_map<int, Foo *>::iterator ir = myMap.begin(); ir != myMap.end(); ++ir ) { delete ir->second; // delete all the (Foo *) values. } (I've found Boost's checked_delete, but I'm not sure how to apply that to the pair<int, Foo *> that the iterator represents). (Also, for the purposes of this question, ignore the fact that storing raw pointers that need deleting in an STL container isn't very sensible).

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  • JQuery Tabs; Google Map is shown with just one tile

    - by java_dude
    Yes this problem is common and I have seen numerous solution on this site but none of them were helpful. I know that re-sizing will fix the problem. Not a jQuery expert and I don't know how to re-size the map after the page has been loaded and Headline 3 is active. I have created a JFiddle example. Any help is appreciated. http://jsfiddle.net/KhwZS/1300/ Thanks Ignore the top comment and the links provided by @Dr.Molle as these links do not provide the solution that I have been looking for, check out the solution I have accepted.

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  • How do I map a macro across a list in Scheme?

    - by josh
    I have a Scheme macro and a long list, and I'd like to map the macro across the list, just as if it were a function. How can I do that using R5RS? The macro accepts several arguments: (mac a b c d) The list has (define my-list ((a1 b1 c1 d1) (a2 b2 c2 d2) ... (an bn cn dn))) And I'd like to have this: (begin (mac a1 b1 c1 d2) (mac a2 b2 c2 d2) ... (mac an bn cn dn)) (By the way, as you can see I'd like to splice the list of arguments too)

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  • Is it possible to use AutoMapper to map methods?

    - by Woj
    I have two classes: public class TestClass1 { public int TestInt { get; set; } public void TestMethod() { // Do something } } public class TestClass2 { public int TestInt { get; set; } public void TestMethod() { // Do something } } I want to create interface that I can use for both classes. The easiest solution is to implement the interface on TestClass1 and TestClass2 but I don;t have access to the implementation of these classes (external dll). I was wondering if I can create new interface and use AutoMapper to map TestClass1 and TestClass2 to ITestInterface: public interface ITestInterface { int TestInt { get; set; } void TestMethod(); }

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  • How to map a set of text as a whole to a node?

    - by JIpeng Tan
    Suppose I have a plain text file with the following data: DataSetOne <br /> content <br /> content <br /> content <br /> DataSetTwo <br /> content <br /> content <br /> content <br /> content <br /> ...and so on... What I want to to is: count how many contents in each data set. For example the result should be <DataSetOne, 3>, <DataSetTwo, 4> I am a beginer to hadoop, I wonder if there is a way to map a chunk of data as a whole to a node. for example, set all DataSetOne to node 1 and all DataSetTwo to node 2. Does anyone can give me an idea how to archive this?

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  • HashMap "WriteOnce" Implementation .. need help

    - by JavaNewbie
    import java.util.*; public class HashMapExample { public static class WriteOnceMap<K, V> extends HashMap<K, V> { public V put(K key, V value) { /* WriteOnceMap is a map that does not allow changing value for a particular key. It means that put() method should throw IllegalArgumentException if the key is already assosiated with some value in the map. Please implement this method to conform to the above description of WriteOnceMap. */ } public void putAll(Map<? extends K, ? extends V> m) { /* Pleaase implement this method to conform to the description of WriteOnceMap above. It should either (1) copy all of the mappings from the specified map to this map or (2) throw IllegalArgumentException and leave this map intact if the parameter already contains some keys from this map. */ } } }

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  • Blend for Visual Studio 2013 Prototyping Applications with SketchFlow

    - by T
    Originally posted on: http://geekswithblogs.net/tburger/archive/2014/08/10/blend-for-visual-studio-2013-prototyping-applications-with-sketchflow.aspxSketchFlow enables rapid creating of dynamic interface mockups very quickly. The SketchFlow workspace is the same as the standard Blend workspace with the inclusion of three panels: the SketchFlow Feedback panel, the SketchFlow Animation panel and the SketchFlow Map panel. By using SketchFlow to prototype, you can get feedback early in the process. It helps to surface possible issues, lower development iterations, and increase stakeholder buy in. SketchFlow prototypes not only provide an initial look but also provide a way to add additional ideas and input and make sure the team is on track prior to investing in complete development. When you have completed the prototyping, you can discard the prototype and just use the lessons learned to design the application from or extract individual elements from your prototype and include them in the application. I don’t recommend trying to transition the entire project into a development project. Objects that you add with the SketchFlow style have a hand-sketched look. The sketch style is used to remind stakeholders that this is a prototype. This encourages them to focus on the flow and functionality without getting distracted by design details. The sketchflow assets are under sketchflow in the asset panel and are identifiable by the postfix “–Sketch”. For example “Button-Sketch”. You can mix sketch and standard controls in your interface, if required. Be creative, if there is a missing control or your interface has a different look and feel than the out of the box one, reuse other sketch controls to mimic the functionality or look and feel. Only use standard controls if it doesn’t distract from the idea that this is a prototype and not a standard application. The SketchFlow Map panel provides information about the structure of your application. To create a new screen in your prototype: Right-click the map surface and choose “Create a Connected Screen”. Name the screens with names that are meaningful to the stakeholders. The start screen is the one that has the green arrow. To change the start screen, right click on any other screen and set to start screen. Only one screen can be the start screen at a time. Rounded screen are component screens to mimic reusable custom controls that will be built into the final application. You can change the colors of all of the boxes and should use colors to create functional groupings. The groupings can be identified in the SketchFlow Project Settings. To add connections between screens in the SketchFlow Map panel. Move the mouse over a screen in the SketchFlow and a menu will appear at the bottom of the screen node. In the menu, click Connect to an existing screen. Drag the arrow to another screen on the Map. You add navigation to your prototype by adding connections on the SketchFlow map or by adding navigation directly to items on your interface. To add navigation from objects on the artboard, right click the item then from the menu, choose “Navigate to”. This will expose a sub-menu with available screens, backward, or forward. When the map has connected screens, the SketchFlow Player displays the connected screens on the Navigate sidebar. All screens show in the SketchFlow Player Map. To see the SketchFlow Player, run your SketchFlow prototype. The Navigation sidebar is meant to show the desired user work flow. The map can be used to view the different screens regardless of suggested navigation in the navigation bar. The map is able to be hidden and shown. As mentioned, a component screen is a shared screen that is used in more than one screen and generally represents what will be a custom object in the application. To create a component screen, you can create a screen, right click on it in the SketchFlow Map and choose “Make into component screen”. You can mouse over a screen and from the menu that appears underneath, choose create and insert component screen. To use an existing screen, select if from the Asset panel under SketchFlow, Components. You can use Storyboards and Visual State animations in your SketchFlow project. However, SketchFlow also offers its own animation technique that is simpler and better suited for prototyping. The SketchFlow Animation panel is above your artboard by default. In SketchFlow animation, you create frames and then position the elements on your interface for each frame. You then specify elapsed time and any effects you want to apply to the transition. The + at the top is what creates new frames. Once you have a new Frame, select it and change the property you want to animate. In the example above, I changed the Text of the result box. You can adjust the time between frames in the lower area between the frames. The easing and effects functions are changed in the center between each frame. You edit the hold time for frames by clicking the clock icon in the lower left and the hold time will appear on each frame and can be edited. The FluidLayout icon (also located in the lower left) will create smooth transitions. Next to the FluidLayout icon is the name of that Animation. You can rename the animation by clicking on it and editing the name. The down arrow chevrons next to the name allow you to view the list of all animations in this prototype and select them for editing. To add the animation to the interface object (such as a button to start the animation), select the PlaySketchFlowAnimationAction from the SketchFlow behaviors in the Assets menu and drag it to an object on your interface. With the PlaySketchFlowAnimationAction that you just added selected in the Objects and Timeline, edit the properties to change the EventName to the event you want and choose the SketchFlowAnimation you want from the drop down list. You may want to add additional information to your screens that isn’t really part of the prototype but is relevant information or a request for clarification or feedback from the reviewer. You do this with annotations or notes. Both appear on the user interface, however, annotations can be switched on or off at design and review time. Notes cannot be switched off. To add an Annotation, chose the Create Annotation from the Tools menu. The annotation appears on the UI where you will add the notes. To display or Hide annotations, click the annotation toggle at the bottom right on the artboard . After to toggle annotations on, the identifier of the person who created them appears on the artboard and you must click that to expand the notes. To add a note to the artboard, simply select the Note-Sketch from Assets ->SketchFlow ->Styles ->Sketch Styles. Drag and drop it to the artboard and place where you want it. When you are ready for users to review the prototype, you have a few options available. Click File -> Export and choose one of the options from the list: Publish to Sharepoint, Package SketchFlowProject, Export to Microsoft Word, or Export as Images. I suggest you play with as many of the options as you can to see what they do. Both the Sharepoint and Packaged SketchFlowProject allow you to collect feedback from one or more users that you can import into the project. The user can make notes on the UI and in the Feedback area in the bottom left corner of the player. When the user is done adding feedback, it is exported from the right most folder icon in the My Feedback panel. Feeback is imported on a panel named SketchFlow Feedback. To get that panel to show up, select Window -> SketchFlow Feedback. Once you have the panel showing, click the + in the upper right of the panel and find the notes you exported. When imported, they will show up in a list and on the artboard. To document your prototype, use the Export to Microsoft Word option from the File menu. That should get you started with prototyping.

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  • SSH Public Key Authentication only works if active session exists before

    - by Webx10
    I have a rather strange problem with my SSH configuration. I set up my server with the help of a Remote Access Card and configured everything with a KVM viewer. So while being logged into the server via the KVM Viewer I configured SSH with only pubkey and tried to login from my local laptop. It worked fine. If I quit the KVM Session (or logout with the user in the KVM session) I cannot login via ssh anymore (pubkey denied). SSH login only works as long as the user is somewhere still logged in. Any hints what the problem might be? Console output for a failed login (all personal data exchanged): OpenSSH_6.2p2, OSSLShim 0.9.8r 8 Dec 2011 debug1: Reading configuration data /Users/mylocaluser/.ssh/config debug1: Reading configuration data /etc/ssh_config debug1: /etc/ssh_config line 20: Applying options for * debug1: /etc/ssh_config line 103: Applying options for * debug1: Connecting to 100.100.100.100 [100.100.100.100] port 12345. debug1: Connection established. debug1: identity file /Users/mylocaluser/.ssh/id_rsa type 1 debug1: identity file /Users/mylocaluser/.ssh/id_rsa-cert type -1 debug1: identity file /Users/mylocaluser/.ssh/id_dsa type -1 debug1: identity file /Users/mylocaluser/.ssh/id_dsa-cert type -1 debug1: Enabling compatibility mode for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_6.2 debug1: Remote protocol version 2.0, remote software version OpenSSH_6.6.1p1 Ubuntu-2ubuntu2 debug1: match: OpenSSH_6.6.1p1 Ubuntu-2ubuntu2 pat OpenSSH* debug1: SSH2_MSG_KEXINIT sent debug1: SSH2_MSG_KEXINIT received debug1: kex: server->client aes128-ctr [email protected] none debug1: kex: client->server aes128-ctr [email protected] none debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP debug1: SSH2_MSG_KEX_DH_GEX_INIT sent debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY debug1: Server host key: RSA ab:12:23:34:45:56:67:78:89:90:12:23:34:45:56:67 debug1: Host '[100.100.100.100]:12345' is known and matches the RSA host key. debug1: Found key in /Users/mylocaluser/.ssh/known_hosts:36 debug1: ssh_rsa_verify: signature correct debug1: SSH2_MSG_NEWKEYS sent debug1: expecting SSH2_MSG_NEWKEYS debug1: SSH2_MSG_NEWKEYS received debug1: Roaming not allowed by server debug1: SSH2_MSG_SERVICE_REQUEST sent debug1: SSH2_MSG_SERVICE_ACCEPT received debug1: Authentications that can continue: publickey debug1: Next authentication method: publickey debug1: Offering RSA public key: /Users/mylocaluser/.ssh/id_rsa debug1: Authentications that can continue: publickey debug1: Offering RSA public key: /Users/mylocaluser/.ssh/id_rsa2 debug1: Authentications that can continue: publickey debug1: Trying private key: /Users/mylocaluser/.ssh/id_dsa debug1: No more authentication methods to try. Permission denied (publickey). Console output for a successfull login (only possible while "active session" exists): OpenSSH_6.2p2, OSSLShim 0.9.8r 8 Dec 2011 debug1: Reading configuration data /Users/mylocaluser/.ssh/config debug1: Reading configuration data /etc/ssh_config debug1: /etc/ssh_config line 20: Applying options for * debug1: /etc/ssh_config line 103: Applying options for * debug1: Connecting to 100.100.100.100 [100.100.100.100] port 12345. debug1: Connection established. debug1: identity file /Users/mylocaluser/.ssh/id_rsa type 1 debug1: identity file /Users/mylocaluser/.ssh/id_rsa-cert type -1 debug1: identity file /Users/mylocaluser/.ssh/id_dsa type -1 debug1: identity file /Users/mylocaluser/.ssh/id_dsa-cert type -1 debug1: Enabling compatibility mode for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_6.2 debug1: Remote protocol version 2.0, remote software version OpenSSH_6.6.1p1 Ubuntu-2ubuntu2 debug1: match: OpenSSH_6.6.1p1 Ubuntu-2ubuntu2 pat OpenSSH* debug1: SSH2_MSG_KEXINIT sent debug1: SSH2_MSG_KEXINIT received debug1: kex: server->client aes128-ctr [email protected] none debug1: kex: client->server aes128-ctr [email protected] none debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP debug1: SSH2_MSG_KEX_DH_GEX_INIT sent debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY debug1: Server host key: RSA ab:12:23:34:45:56:67:78:89:90:12:23:34:45:56:67 debug1: Host '[100.100.100.100]:12345' is known and matches the RSA host key. debug1: Found key in /Users/mylocaluser/.ssh/known_hosts:36 debug1: ssh_rsa_verify: signature correct debug1: SSH2_MSG_NEWKEYS sent debug1: expecting SSH2_MSG_NEWKEYS debug1: SSH2_MSG_NEWKEYS received debug1: Roaming not allowed by server debug1: SSH2_MSG_SERVICE_REQUEST sent debug1: SSH2_MSG_SERVICE_ACCEPT received debug1: Authentications that can continue: publickey debug1: Next authentication method: publickey debug1: Offering RSA public key: /Users/mylocaluser/.ssh/id_rsa debug1: Server accepts key: pkalg ssh-rsa blen 279 debug1: Authentication succeeded (publickey). Authenticated to 100.100.100.100 ([100.100.100.100]:12345). debug1: channel 0: new [client-session] debug1: Requesting [email protected] debug1: Entering interactive session. debug1: Sending environment. debug1: Sending env LANG = de_DE.UTF-8 Welcome to Ubuntu 14.04.1 LTS

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  • Inheritance Mapping Strategies with Entity Framework Code First CTP5: Part 3 – Table per Concrete Type (TPC) and Choosing Strategy Guidelines

    - by mortezam
    This is the third (and last) post in a series that explains different approaches to map an inheritance hierarchy with EF Code First. I've described these strategies in previous posts: Part 1 – Table per Hierarchy (TPH) Part 2 – Table per Type (TPT)In today’s blog post I am going to discuss Table per Concrete Type (TPC) which completes the inheritance mapping strategies supported by EF Code First. At the end of this post I will provide some guidelines to choose an inheritance strategy mainly based on what we've learned in this series. TPC and Entity Framework in the Past Table per Concrete type is somehow the simplest approach suggested, yet using TPC with EF is one of those concepts that has not been covered very well so far and I've seen in some resources that it was even discouraged. The reason for that is just because Entity Data Model Designer in VS2010 doesn't support TPC (even though the EF runtime does). That basically means if you are following EF's Database-First or Model-First approaches then configuring TPC requires manually writing XML in the EDMX file which is not considered to be a fun practice. Well, no more. You'll see that with Code First, creating TPC is perfectly possible with fluent API just like other strategies and you don't need to avoid TPC due to the lack of designer support as you would probably do in other EF approaches. Table per Concrete Type (TPC)In Table per Concrete type (aka Table per Concrete class) we use exactly one table for each (nonabstract) class. All properties of a class, including inherited properties, can be mapped to columns of this table, as shown in the following figure: As you can see, the SQL schema is not aware of the inheritance; effectively, we’ve mapped two unrelated tables to a more expressive class structure. If the base class was concrete, then an additional table would be needed to hold instances of that class. I have to emphasize that there is no relationship between the database tables, except for the fact that they share some similar columns. TPC Implementation in Code First Just like the TPT implementation, we need to specify a separate table for each of the subclasses. We also need to tell Code First that we want all of the inherited properties to be mapped as part of this table. In CTP5, there is a new helper method on EntityMappingConfiguration class called MapInheritedProperties that exactly does this for us. Here is the complete object model as well as the fluent API to create a TPC mapping: public abstract class BillingDetail {     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } }          public class BankAccount : BillingDetail {     public string BankName { get; set; }     public string Swift { get; set; } }          public class CreditCard : BillingDetail {     public int CardType { get; set; }     public string ExpiryMonth { get; set; }     public string ExpiryYear { get; set; } }      public class InheritanceMappingContext : DbContext {     public DbSet<BillingDetail> BillingDetails { get; set; }              protected override void OnModelCreating(ModelBuilder modelBuilder)     {         modelBuilder.Entity<BankAccount>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("BankAccounts");         });         modelBuilder.Entity<CreditCard>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("CreditCards");         });                 } } The Importance of EntityMappingConfiguration ClassAs a side note, it worth mentioning that EntityMappingConfiguration class turns out to be a key type for inheritance mapping in Code First. Here is an snapshot of this class: namespace System.Data.Entity.ModelConfiguration.Configuration.Mapping {     public class EntityMappingConfiguration<TEntityType> where TEntityType : class     {         public ValueConditionConfiguration Requires(string discriminator);         public void ToTable(string tableName);         public void MapInheritedProperties();     } } As you have seen so far, we used its Requires method to customize TPH. We also used its ToTable method to create a TPT and now we are using its MapInheritedProperties along with ToTable method to create our TPC mapping. TPC Configuration is Not Done Yet!We are not quite done with our TPC configuration and there is more into this story even though the fluent API we saw perfectly created a TPC mapping for us in the database. To see why, let's start working with our object model. For example, the following code creates two new objects of BankAccount and CreditCard types and tries to add them to the database: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount();     CreditCard creditCard = new CreditCard() { CardType = 1 };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Running this code throws an InvalidOperationException with this message: The changes to the database were committed successfully, but an error occurred while updating the object context. The ObjectContext might be in an inconsistent state. Inner exception message: AcceptChanges cannot continue because the object's key values conflict with another object in the ObjectStateManager. Make sure that the key values are unique before calling AcceptChanges. The reason we got this exception is because DbContext.SaveChanges() internally invokes SaveChanges method of its internal ObjectContext. ObjectContext's SaveChanges method on its turn by default calls AcceptAllChanges after it has performed the database modifications. AcceptAllChanges method merely iterates over all entries in ObjectStateManager and invokes AcceptChanges on each of them. Since the entities are in Added state, AcceptChanges method replaces their temporary EntityKey with a regular EntityKey based on the primary key values (i.e. BillingDetailId) that come back from the database and that's where the problem occurs since both the entities have been assigned the same value for their primary key by the database (i.e. on both BillingDetailId = 1) and the problem is that ObjectStateManager cannot track objects of the same type (i.e. BillingDetail) with the same EntityKey value hence it throws. If you take a closer look at the TPC's SQL schema above, you'll see why the database generated the same values for the primary keys: the BillingDetailId column in both BankAccounts and CreditCards table has been marked as identity. How to Solve The Identity Problem in TPC As you saw, using SQL Server’s int identity columns doesn't work very well together with TPC since there will be duplicate entity keys when inserting in subclasses tables with all having the same identity seed. Therefore, to solve this, either a spread seed (where each table has its own initial seed value) will be needed, or a mechanism other than SQL Server’s int identity should be used. Some other RDBMSes have other mechanisms allowing a sequence (identity) to be shared by multiple tables, and something similar can be achieved with GUID keys in SQL Server. While using GUID keys, or int identity keys with different starting seeds will solve the problem but yet another solution would be to completely switch off identity on the primary key property. As a result, we need to take the responsibility of providing unique keys when inserting records to the database. We will go with this solution since it works regardless of which database engine is used. Switching Off Identity in Code First We can switch off identity simply by placing DatabaseGenerated attribute on the primary key property and pass DatabaseGenerationOption.None to its constructor. DatabaseGenerated attribute is a new data annotation which has been added to System.ComponentModel.DataAnnotations namespace in CTP5: public abstract class BillingDetail {     [DatabaseGenerated(DatabaseGenerationOption.None)]     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } } As always, we can achieve the same result by using fluent API, if you prefer that: modelBuilder.Entity<BillingDetail>()             .Property(p => p.BillingDetailId)             .HasDatabaseGenerationOption(DatabaseGenerationOption.None); Working With The Object Model Our TPC mapping is ready and we can try adding new records to the database. But, like I said, now we need to take care of providing unique keys when creating new objects: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount()      {          BillingDetailId = 1                          };     CreditCard creditCard = new CreditCard()      {          BillingDetailId = 2,         CardType = 1     };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Polymorphic Associations with TPC is Problematic The main problem with this approach is that it doesn’t support Polymorphic Associations very well. After all, in the database, associations are represented as foreign key relationships and in TPC, the subclasses are all mapped to different tables so a polymorphic association to their base class (abstract BillingDetail in our example) cannot be represented as a simple foreign key relationship. For example, consider the the domain model we introduced here where User has a polymorphic association with BillingDetail. This would be problematic in our TPC Schema, because if User has a many-to-one relationship with BillingDetail, the Users table would need a single foreign key column, which would have to refer both concrete subclass tables. This isn’t possible with regular foreign key constraints. Schema Evolution with TPC is Complex A further conceptual problem with this mapping strategy is that several different columns, of different tables, share exactly the same semantics. This makes schema evolution more complex. For example, a change to a base class property results in changes to multiple columns. It also makes it much more difficult to implement database integrity constraints that apply to all subclasses. Generated SQLLet's examine SQL output for polymorphic queries in TPC mapping. For example, consider this polymorphic query for all BillingDetails and the resulting SQL statements that being executed in the database: var query = from b in context.BillingDetails select b; Just like the SQL query generated by TPT mapping, the CASE statements that you see in the beginning of the query is merely to ensure columns that are irrelevant for a particular row have NULL values in the returning flattened table. (e.g. BankName for a row that represents a CreditCard type). TPC's SQL Queries are Union Based As you can see in the above screenshot, the first SELECT uses a FROM-clause subquery (which is selected with a red rectangle) to retrieve all instances of BillingDetails from all concrete class tables. The tables are combined with a UNION operator, and a literal (in this case, 0 and 1) is inserted into the intermediate result; (look at the lines highlighted in yellow.) EF reads this to instantiate the correct class given the data from a particular row. A union requires that the queries that are combined, project over the same columns; hence, EF has to pad and fill up nonexistent columns with NULL. This query will really perform well since here we can let the database optimizer find the best execution plan to combine rows from several tables. There is also no Joins involved so it has a better performance than the SQL queries generated by TPT where a Join is required between the base and subclasses tables. Choosing Strategy GuidelinesBefore we get into this discussion, I want to emphasize that there is no one single "best strategy fits all scenarios" exists. As you saw, each of the approaches have their own advantages and drawbacks. Here are some rules of thumb to identify the best strategy in a particular scenario: If you don’t require polymorphic associations or queries, lean toward TPC—in other words, if you never or rarely query for BillingDetails and you have no class that has an association to BillingDetail base class. I recommend TPC (only) for the top level of your class hierarchy, where polymorphism isn’t usually required, and when modification of the base class in the future is unlikely. If you do require polymorphic associations or queries, and subclasses declare relatively few properties (particularly if the main difference between subclasses is in their behavior), lean toward TPH. Your goal is to minimize the number of nullable columns and to convince yourself (and your DBA) that a denormalized schema won’t create problems in the long run. If you do require polymorphic associations or queries, and subclasses declare many properties (subclasses differ mainly by the data they hold), lean toward TPT. Or, depending on the width and depth of your inheritance hierarchy and the possible cost of joins versus unions, use TPC. By default, choose TPH only for simple problems. For more complex cases (or when you’re overruled by a data modeler insisting on the importance of nullability constraints and normalization), you should consider the TPT strategy. But at that point, ask yourself whether it may not be better to remodel inheritance as delegation in the object model (delegation is a way of making composition as powerful for reuse as inheritance). Complex inheritance is often best avoided for all sorts of reasons unrelated to persistence or ORM. EF acts as a buffer between the domain and relational models, but that doesn’t mean you can ignore persistence concerns when designing your classes. SummaryIn this series, we focused on one of the main structural aspect of the object/relational paradigm mismatch which is inheritance and discussed how EF solve this problem as an ORM solution. We learned about the three well-known inheritance mapping strategies and their implementations in EF Code First. Hopefully it gives you a better insight about the mapping of inheritance hierarchies as well as choosing the best strategy for your particular scenario. Happy New Year and Happy Code-Firsting! References ADO.NET team blog Java Persistence with Hibernate book a { color: #5A99FF; } a:visited { color: #5A99FF; } .title { padding-bottom: 5px; font-family: Segoe UI; font-size: 11pt; font-weight: bold; padding-top: 15px; } .code, .typeName { font-family: consolas; } .typeName { color: #2b91af; } .padTop5 { padding-top: 5px; } .padTop10 { padding-top: 10px; } .exception { background-color: #f0f0f0; font-style: italic; padding-bottom: 5px; padding-left: 5px; padding-top: 5px; padding-right: 5px; }

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  • Unable to SSH into EC2 instance on Fedora 17

    - by abhishek
    I did following steps But I am not able to SSH to it(Same steps work fine on Fedora 14 image). I am getting Permission denied (publickey,gssapi-keyex,gssapi-with-mic) I created new instance using fedora 17 amazon community image(ami-2ea50247). I copied my ssh keys under /home/usertest/.ssh/ after creating a usertest I have SELINUX=disabled here is Debug info: $ ssh -vvv ec2-54-243-101-41.compute-1.amazonaws.com ssh -vvv ec2-54-243-101-41.compute-1.amazonaws.com OpenSSH_5.2p1, OpenSSL 1.0.0b-fips 16 Nov 2010 debug1: Reading configuration data /etc/ssh/ssh_config debug1: Applying options for * debug2: ssh_connect: needpriv 0 debug1: Connecting to ec2-54-243-101-41.compute-1.amazonaws.com [54.243.101.41] port 22. debug1: Connection established. debug1: identity file /home/usertest/.ssh/identity type -1 debug1: identity file /home/usertest/.ssh/id_rsa type -1 debug3: Not a RSA1 key file /home/usertest/.ssh/id_dsa. debug2: key_type_from_name: unknown key type '-----BEGIN' debug3: key_read: missing keytype debug2: key_type_from_name: unknown key type 'Proc-Type:' debug3: key_read: missing keytype debug2: key_type_from_name: unknown key type 'DEK-Info:' debug3: key_read: missing keytype debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug2: key_type_from_name: unknown key type '-----END' debug3: key_read: missing keytype debug1: identity file /home/usertest/.ssh/id_dsa type 2 debug1: Remote protocol version 2.0, remote software version OpenSSH_5.9 debug1: match: OpenSSH_5.9 pat OpenSSH* debug1: Enabling compatibility mode for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_5.2 debug2: fd 3 setting O_NONBLOCK debug1: SSH2_MSG_KEXINIT sent debug1: SSH2_MSG_KEXINIT received debug2: kex_parse_kexinit: diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1 debug2: kex_parse_kexinit: ssh-rsa,ssh-dss debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected] debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected] debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96 debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96 debug2: kex_parse_kexinit: none,[email protected],zlib debug2: kex_parse_kexinit: none,[email protected],zlib debug2: kex_parse_kexinit: debug2: kex_parse_kexinit: debug2: kex_parse_kexinit: first_kex_follows 0 debug2: kex_parse_kexinit: reserved 0 debug2: kex_parse_kexinit: diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1 debug2: kex_parse_kexinit: ssh-rsa,ssh-dss debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected] debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected] debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-sha2-256,hmac-sha2-256-96,hmac-sha2-512,hmac-sha2-512-96,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96 debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-sha2-256,hmac-sha2-256-96,hmac-sha2-512,hmac-sha2-512-96,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96 debug2: kex_parse_kexinit: none,[email protected] debug2: kex_parse_kexinit: none,[email protected] debug2: kex_parse_kexinit: debug2: kex_parse_kexinit: debug2: kex_parse_kexinit: first_kex_follows 0 debug2: kex_parse_kexinit: reserved 0 debug2: mac_setup: found hmac-md5 debug1: kex: server->client aes128-ctr hmac-md5 none debug2: mac_setup: found hmac-md5 debug1: kex: client->server aes128-ctr hmac-md5 none debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP debug2: dh_gen_key: priv key bits set: 131/256 debug2: bits set: 506/1024 debug1: SSH2_MSG_KEX_DH_GEX_INIT sent debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY debug3: check_host_in_hostfile: filename /home/usertest/.ssh/known_hosts debug3: check_host_in_hostfile: match line 17 debug3: check_host_in_hostfile: filename /home/usertest/.ssh/known_hosts debug3: check_host_in_hostfile: match line 17 debug1: Host 'ec2-54-243-101-41.compute-1.amazonaws.com' is known and matches the RSA host key. debug1: Found key in /home/usertest/.ssh/known_hosts:17 debug2: bits set: 500/1024 debug1: ssh_rsa_verify: signature correct debug2: kex_derive_keys debug2: set_newkeys: mode 1 debug1: SSH2_MSG_NEWKEYS sent debug1: expecting SSH2_MSG_NEWKEYS debug2: set_newkeys: mode 0 debug1: SSH2_MSG_NEWKEYS received debug1: SSH2_MSG_SERVICE_REQUEST sent debug2: service_accept: ssh-userauth debug1: SSH2_MSG_SERVICE_ACCEPT received debug2: key: /home/usertest/.ssh/identity ((nil)) debug2: key: /home/usertest/.ssh/id_rsa ((nil)) debug2: key: /home/usertest/.ssh/id_dsa (0x7f904b5ae260) debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic debug3: start over, passed a different list publickey,gssapi-keyex,gssapi-with-mic debug3: preferred gssapi-with-mic,publickey,keyboard-interactive,password debug3: authmethod_lookup gssapi-with-mic debug3: remaining preferred: publickey,keyboard-interactive,password debug3: authmethod_is_enabled gssapi-with-mic debug1: Next authentication method: gssapi-with-mic debug3: Trying to reverse map address 54.243.101.41. debug1: Unspecified GSS failure. Minor code may provide more information Credentials cache file '/tmp/krb5cc_500' not found debug1: Unspecified GSS failure. Minor code may provide more information Credentials cache file '/tmp/krb5cc_500' not found debug1: Unspecified GSS failure. Minor code may provide more information debug2: we did not send a packet, disable method debug3: authmethod_lookup publickey debug3: remaining preferred: keyboard-interactive,password debug3: authmethod_is_enabled publickey debug1: Next authentication method: publickey debug1: Trying private key: /home/usertest/.ssh/identity debug3: no such identity: /home/usertest/.ssh/identity debug1: Trying private key: /home/usertest/.ssh/id_rsa debug3: no such identity: /home/usertest/.ssh/id_rsa debug1: Offering public key: /home/usertest/.ssh/id_dsa debug3: send_pubkey_test debug2: we sent a publickey packet, wait for reply debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic debug2: we did not send a packet, disable method debug1: No more authentication methods to try. Permission denied (publickey,gssapi-keyex,gssapi-with-mic).

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  • how do I have a windows group automatically map a drive on connection?

    - by Eric Martin
    I have 3 different windows user groups. Each group needs to have a certain drive mapped, unique to that group. Is there a way to say x group maps to y drive every time they connect? If I put something in their start up, that's a lot of manual work. I am needing something that I have set per user group, if possible. If this is not feasible, is there another option? Thanks again for the help! Eric

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  • How to map DNS with my new IP address? [closed]

    - by Carsen
    I have installed apache2 in my ubuntu server. In apache2.conf, i have specified this <VirtualHost *:80> ServerName something.in DocumentRoot somewhere/public <Directory somewhere/public> AllowOverride all Options -MultiViews </Directory> </VirtualHost> Also, i have my Domain - something.in registered with Go Daddy. There i have changed A(HOST) to point to XXX.XXX.XX.XXX which is my public address. But when i type something.in in browser, i am not getting my apps home page. I got my public IP address as "XXX.XXX.XX.XXX is Natted to XX.XX.X.XX". which IP address should i use in my DNS settings? How to make apache2 in my ubuntu server listen to request for something.in?

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  • How to map a key to a file explorer shell extension?

    - by Tony_Henrich
    I have a file explorer shell extension called "Copy File Path" or "Copy Folder Path", depending on which pane I am in in file explorer, which copies the full path of a file or a folder to the clipboard. Because it's very handy for me, I use it many times during the day. To make it more productive, I would like to assign a function key to it instead of using the right mouse click context menu, looking for it in the menu (big menu because of many extensions) and selecting it. The way I want to use it is select the file with the mouse and hit the function key. Is there a utility or tool, tray taskmaybe, which can add this functionality to Windows?

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  • Is there a way to map a local drive letter in a Virtual PC Guest O/S to a host drive?

    - by Clay Nichols
    I have a bunch of programming projects on my P:\ drive (on Windows 7) I'm now doing some programming within Virtual PC Windows XP Mode and I'd like to "call" that drive, within the Win XP guest, the P: drive. I've mapped drive letter P: to "network" drive on the Host but that goes across the network so it's very slow. I tried using the SUBST command but it wouldn't take the \tsclients\p as a parameter. Basically, the command line interpreter (is that DOS on Win 7 ??) doesn't recognize that directory (\tsclients\p)

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  • Change Audio title from English to Sinhalese using ffmpeg

    - by user330461
    I insert an extra Sound track in my video file and it works well. ffmpeg -i news.mov -i news.wav -map 0:0 -map 0:1 -map 1:0 -pass 1 -vcodec libx264 -preset fast -b 512k -minrate 512k -maxrate 512k -bufsize 512k -threads 0 -f mp4 -an -y /dev/null && ffmpeg -i news.mov -i news.wav -map 0:0 -map 0:1 -map 1:0 -pass 2 -acodec libfaac -ab 128k -ac 2 -vcodec libx264 -preset fast -b 512k -minrate 512k -maxrate 512k -bufsize 512k -threads 0 -f mp4 news.mp4 The default audio track come with the label "English" and I would like to give it a label "Sinhalese" The Second Audio track come up without a label as "track#1" and I would like to give that a label of "Tamil". How do I do that ?

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  • How to map a user to a domain, with Usermin and Postfix?

    - by HappyDeveloper
    What I need is to create a couple of websites, each one with only one user, which is allowed to send mails from any address @ his own domain. Example: Site foo.com would have an user foo, which can send mails from [email protected]. Currently, when the user logins to Usermin, the default 'from' field is example-dns.net (editable) I want it to show an editable field for the user part, and @foo.com (non editable) So how can I do this? Is there some way to automate this?

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  • How to map a user to a domain, with Usermin and Postfix?

    - by HappyDeveloper
    What I need is to create a couple of websites, each one with only one user, which is allowed to send mails from any address @ his own domain. Example: Site foo.com would have an user foo, which can send mails from [email protected]. Currently, when the user logins to Usermin, the default 'from' field is example-dns.net (editable) I want it to show an editable field for the user part, and @foo.com (non editable) So how can I do this? Is there some way to automate this?

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  • Why is it bad to map network drives in Windows?

    - by Beeblebrox
    There has been some spirited discussion within our IT department about mapping network drives. In particular, it has been said that mapping network drives is A Bad Thing and that adding DFS paths or network shares to your (Windows Explorer/Libraries) Favourites is a far better solution. Why is this the case? Personally I find the convenience of z:\folder to be better than \\server\path\folder', particularly with cmd line and scripting (of course I'm not talking about hard-coded links, naturally!). I have tried searching for pros and cons of mapped network drives, but I haven't seen anything other than 'should the network go down, the drive will be unavailable'. But this is a limitation of any network-accessed storage... I have also been told that mapped network drives poll the network when the network resource is unavailable, however I haven't found more information on this. Wouldn't this still be an issue with other network access mechanisms (that is, mapped Favourites) whenever Windows tries to enumerate the file system (for example, when a file/folder picker dialog is opened)? -- Do network drives poll the network any more than a Windows Explorer library/favourite?

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  • How do you map a solo press of a modifier key to its own function or mapping on Windows?

    - by Conrad.Dean
    Today on hacker news there was a clever article on custom shortcut keys. The author talks about a technique for remapping a modifier key such as CTRL to ESC if CTRL were pressed without a modifier. This is useful in vim because of how often you need to press ESC. Another technique he describes is mapping the open parenthesis, ( to the left shift key, and ) to the right shift key. If another key is pressed when shift is held down, the shift key behaves normally. The author describes the software he uses on OSX, but is there a way to do this on Windows? I've heard of AutoHotKey but it seems to only fire macros when simple keys are pressed, rather than the conditional state switch that this would require.

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  • pam auth via winbind, howto map primary group for users?

    - by dr gonzo
    I have unix users authenticating to an PDC (via winbind) and want to have the primary group of those users a local unix group (e.g. www-data). users have the group "domain users" with gid 10006 (as the gid winbind mapping) idmap uid = 10000-20000 idmap gid = 10000-20000 winbind enum groups = yes winbind enum users = yes winbind use default domain = yes winbind nested groups = yes but want that the primary group is 33 for all users (www-data) how to achieve that?

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  • How can I map my server's IP address to my domain?

    - by samoz
    I rented some server space from a new host and have a static IP address and a domain name that I previously purchased, but I do not know how to register the domain name to point to my server. My previous host did this for me, but my new host only offers hardware, i.e. they won't do it for me. How can I register a domain name I own to point to my server's IP address?

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