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• Vote of Disconfidence to Entity Framework

  - by Ricardo Peres

  A friend of mine has found the following problem with Entity Framework 4: Two simple classes and one association between them (one to many): One condition to filter out soft-deleted entities (WHERE Deleted = 0): 100 records in the database; A simple query: 1: var l = ctx.Person.Include("Address").Where(x => (x.Address.Name == "317 Oak Blvd." && x.Address.Number == 926) || (x.Address.Name == "891 White Milton Drive" && x.Address.Number == 497)); Will produce the following SQL: 1: SELECT 2: [Extent1].[Id] AS [Id], 3: [Extent1].[FullName] AS [FullName], 4: [Extent1].[AddressId] AS [AddressId], 5: [Extent202].[Id] AS [Id1], 6: [Extent202].[Name] AS [Name], 7: [Extent202].[Number] AS [Number] 8: FROM [dbo].[Person] AS [Extent1] 9: LEFT OUTER JOIN [dbo].[Address] AS [Extent2] ON ([Extent2].[Deleted] = 0) AND ([Extent1].[AddressId] = [Extent2].[Id]) 10: LEFT OUTER JOIN [dbo].[Address] AS [Extent3] ON ([Extent3].[Deleted] = 0) AND ([Extent1].[AddressId] = [Extent3].[Id]) 11: LEFT OUTER JOIN [dbo].[Address] AS [Extent4] ON ([Extent4].[Deleted] = 0) AND ([Extent1].[AddressId] = [Extent4].[Id]) 12: LEFT OUTER JOIN [dbo].[Address] AS [Extent5] ON ([Extent5].[Deleted] = 0) AND ([Extent1].[AddressId] = [Extent5].[Id]) 13: LEFT OUTER JOIN [dbo].[Address] AS [Extent6] ON ([Extent6].[Deleted] = 0) AND ([Extent1].[AddressId] = [Extent6].[Id]) 14: ... 15: WHERE ((N'317 Oak Blvd.' = [Extent2].[Name]) AND (926 = [Extent3].[Number])) 16: ... And will result in 680 MB of memory being taken! Now, Entity Framework has been historically known for producing less than optimal SQL, but 680 MB for 100 entities?! According to Microsoft, the problem will be addressed in the following version, there is a Connect issue open. There is even a whitepaper, Performance Considerations for Entity Framework 5, which talks about some of the changes and optimizations coming on version 5, but by reading it, I got even more concerned: “Once the cache contains a set number of entries (800), we start a timer that periodically (once-per-minute) sweeps the cache.” Say what?! The next version of Entity Framework will spawn timer threads?! When Code First came along, I thought it was a step in the right direction. Sure, it didn’t include some things that NHibernate did for quite some time – for example, different strategies for Id generation that do not rely on IDENTITY columns, which makes INSERT batching impossible, or support for enumerated types – but I thought these would come with the time. Now, enumerated types have, but so did… timer threads! I’m afraid Entity Framework is becoming a monster.

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• Hibernate unknown entity (not missing @Entity or import javax.persistence.Entity )

  - by david99world

  I've got a really simple class... import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.Table; @Entity @Table(name = "users") public class User { @Column(name = "firstName") private String firstName; @Column(name = "lastName") private String lastName; @Column(name = "email") private String email; @Id @GeneratedValue(strategy=GenerationType.AUTO) @Column(name = "id") private long id; public String getFirstName() { return firstName; } public void setFirstName(String firstName) { this.firstName = firstName; } public String getLastName() { return lastName; } public void setLastName(String lastName) { this.lastName = lastName; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } public long getId() { return id; } public void setId(long id) { this.id = id; } } I call it using... public class Main { /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub HibernateUtil.buildSessionFactory(); Session session = HibernateUtil.getSessionFactory().getCurrentSession(); session.beginTransaction(); User u = new User(); u.setEmail("[email protected]"); u.setFirstName("David"); u.setLastName("Gray"); session.save(u); session.getTransaction().commit(); System.out.println("Record committed"); session.close(); } } I keep getting... Exception in thread "main" org.hibernate.MappingException: Unknown entity: org.assessme.com.entity.User at org.hibernate.internal.SessionFactoryImpl.getEntityPersister(SessionFactoryImpl.java:1172) at org.hibernate.internal.SessionImpl.getEntityPersister(SessionImpl.java:1316) at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:117) at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:204) at org.hibernate.event.internal.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:55) at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:189) at org.hibernate.event.internal.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:49) at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:90) at org.hibernate.internal.SessionImpl.fireSave(SessionImpl.java:670) at org.hibernate.internal.SessionImpl.save(SessionImpl.java:662) at org.hibernate.internal.SessionImpl.save(SessionImpl.java:658) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:601) at org.hibernate.context.internal.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:352) at $Proxy4.save(Unknown Source) at Main.main(Main.java:20) hibernateUtil is... import org.hibernate.SessionFactory; import org.hibernate.cfg.Configuration; import org.hibernate.service.ServiceRegistry; import org.hibernate.service.ServiceRegistryBuilder; public class HibernateUtil { private static SessionFactory sessionFactory; private static ServiceRegistry serviceRegistry; public static SessionFactory buildSessionFactory() { try { // Create the SessionFactory from hibernate.cfg.xml Configuration configuration = new Configuration(); configuration.configure(); serviceRegistry = new ServiceRegistryBuilder().applySettings(configuration.getProperties()).buildServiceRegistry(); return new Configuration().configure().buildSessionFactory(serviceRegistry); } catch (Throwable ex) { // Make sure you log the exception, as it might be swallowed System.err.println("Initial SessionFactory creation failed." + ex); throw new ExceptionInInitializerError(ex); } } public static SessionFactory getSessionFactory() { sessionFactory = new Configuration().configure().buildSessionFactory(serviceRegistry); return sessionFactory; } } does anyone have any ideas as I've looked at so many duplicates but the resolutions don't appear to work for me. hibernate.cfg.xml shown below... <?xml version='1.0' encoding='utf-8'?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <!-- Database connection settings --> <property name="connection.driver_class">com.mysql.jdbc.Driver</property> <property name="connection.url">jdbc:mysql://localhost/ssme</property> <property name="connection.username">root</property> <property name="connection.password">mypassword</property> <!-- JDBC connection pool (use the built-in) --> <property name="connection.pool_size">1</property> <!-- SQL dialect --> <property name="dialect">org.hibernate.dialect.MySQLDialect</property> <!-- Enable Hibernate's automatic session context management --> <property name="current_session_context_class">thread</property> <!-- Disable the second-level cache --> <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property> <!-- Echo all executed SQL to stdout --> <property name="show_sql">true</property> <!-- Drop and re-create the database schema on startup --> <property name="hbm2ddl.auto">update</property> </session-factory> </hibernate-configuration>

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• Entity Framework Complex Type vs Creating new Entity

  - by Ronny

  Hi, I'm reading about the Entity Framework 4.0 and I was wondering why should I create a complex type and not a new Entity (Table) and a relation between them? Thanks, Ronny

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• Reading data from an Entity Framework data model through a WCF Data Service

  - by nikolaosk

  This is going to be the fourth post of a series of posts regarding ASP.Net and the Entity Framework and how we can use Entity Framework to access our datastore. You can find the first one here , the second one here and the third one here . I have a post regarding ASP.Net and EntityDataSource. You can read it here .I have 3 more posts on Profiling Entity Framework applications. You can have a look at them here , here and here . Microsoft with .Net 3.0 Framework, introduced WCF. WCF is Microsoft's...(read more)

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• Data binding in an ASP.Net application with Entity Framework

  - by nikolaosk

  This is going to be the eighth post of a series of posts regarding ASP.Net and the Entity Framework and how we can use Entity Framework to access our datastore. You can find the first one here , the second one here , the third one here , the fourth one here , the fifth one here ,the sixth one here and the seventh one here . I have a post regarding ASP.Net and EntityDataSource . You can read it here .I have 3 more posts on Profiling Entity Framework applications. You can have a look at them here ...(read more)

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• Using stored procedures with Entity Framework in an ASP.Net application

  - by nikolaosk

  This is going to be the third post of a series of posts regarding ASP.Net and the Entity Framework and how we can use Entity Framework to access our datastore. You can find the first one here and the second one here . I have a post regarding ASP.Net and EntityDataSource. You can read it here .I have 3 more posts on Profiling Entity Framework applications. You can have a look at them here , here and here . In this post I will show you how to select,insert,update,delete data in the database using EF...(read more)

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• Creating an Entity Data Model using the Model First approach

  - by nikolaosk

  This is going to be the second post of a series of posts regarding Entity Framework and how we can use Entity Framework version 4.0 new features. You can read the first post here . In order to follow along you must have some knowledge of C# and know what an ORM system is and what kind of problems Entity Framework addresses.It will be handy to know how to work inside the Visual Studio 2010 IDE . I have a post regarding ASP.Net and EntityDataSource . You can read it here .I have 3 more posts on Profiling...(read more)

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• Entity Framework Batch Update and Future Queries

  - by pwelter34

  Entity Framework Extended Library A library the extends the functionality of Entity Framework. Features Batch Update and Delete Future Queries Audit Log Project Package and Source NuGet Package PM> Install-Package EntityFramework.Extended NuGet: http://nuget.org/List/Packages/EntityFramework.Extended Source: http://github.com/loresoft/EntityFramework.Extended Batch Update and Delete A current limitations of the Entity Framework is that in order to update or delete an entity you have to first retrieve it into memory. Now in most scenarios this is just fine. There are however some senerios where performance would suffer. Also, for single deletes, the object must be retrieved before it can be deleted requiring two calls to the database. Batch update and delete eliminates the need to retrieve and load an entity before modifying it. Deleting //delete all users where FirstName matches context.Users.Delete(u => u.FirstName == "firstname"); Update //update all tasks with status of 1 to status of 2 context.Tasks.Update( t => t.StatusId == 1, t => new Task {StatusId = 2}); //example of using an IQueryable as the filter for the update var users = context.Users .Where(u => u.FirstName == "firstname"); context.Users.Update( users, u => new User {FirstName = "newfirstname"}); Future Queries Build up a list of queries for the data that you need and the first time any of the results are accessed, all the data will retrieved in one round trip to the database server. Reducing the number of trips to the database is a great. Using this feature is as simple as appending .Future() to the end of your queries. To use the Future Queries, make sure to import the EntityFramework.Extensions namespace. Future queries are created with the following extension methods... Future() FutureFirstOrDefault() FutureCount() Sample // build up queries var q1 = db.Users .Where(t => t.EmailAddress == "[email protected]") .Future(); var q2 = db.Tasks .Where(t => t.Summary == "Test") .Future(); // this triggers the loading of all the future queries var users = q1.ToList(); In the example above, there are 2 queries built up, as soon as one of the queries is enumerated, it triggers the batch load of both queries. // base query var q = db.Tasks.Where(t => t.Priority == 2); // get total count var q1 = q.FutureCount(); // get page var q2 = q.Skip(pageIndex).Take(pageSize).Future(); // triggers execute as a batch int total = q1.Value; var tasks = q2.ToList(); In this example, we have a common senerio where you want to page a list of tasks. In order for the GUI to setup the paging control, you need a total count. With Future, we can batch together the queries to get all the data in one database call. Future queries work by creating the appropriate IFutureQuery object that keeps the IQuerable. The IFutureQuery object is then stored in IFutureContext.FutureQueries list. Then, when one of the IFutureQuery objects is enumerated, it calls back to IFutureContext.ExecuteFutureQueries() via the LoadAction delegate. ExecuteFutureQueries builds a batch query from all the stored IFutureQuery objects. Finally, all the IFutureQuery objects are updated with the results from the query. Audit Log The Audit Log feature will capture the changes to entities anytime they are submitted to the database. The Audit Log captures only the entities that are changed and only the properties on those entities that were changed. The before and after values are recorded. AuditLogger.LastAudit is where this information is held and there is a ToXml() method that makes it easy to turn the AuditLog into xml for easy storage. The AuditLog can be customized via attributes on the entities or via a Fluent Configuration API. Fluent Configuration // config audit when your application is starting up... var auditConfiguration = AuditConfiguration.Default; auditConfiguration.IncludeRelationships = true; auditConfiguration.LoadRelationships = true; auditConfiguration.DefaultAuditable = true; // customize the audit for Task entity auditConfiguration.IsAuditable<Task>() .NotAudited(t => t.TaskExtended) .FormatWith(t => t.Status, v => FormatStatus(v)); // set the display member when status is a foreign key auditConfiguration.IsAuditable<Status>() .DisplayMember(t => t.Name); Create an Audit Log var db = new TrackerContext(); var audit = db.BeginAudit(); // make some updates ... db.SaveChanges(); var log = audit.LastLog;

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• Entity Framework and Plain Old CLR Objects in an ASP.Net application

  - by nikolaosk

  This is going to be the sixth post of a series of posts regarding ASP.Net and the Entity Framework and how we can use Entity Framework to access our datastore. You can find the first one here , the second one here and the third one here , the fourth one here and the fifth one here . I have a post regarding ASP.Net and EntityDataSource. You can read it here .I have 3 more posts on Profiling Entity Framework applications. You can have a look at them here , here and here . In this post I will be looking...(read more)

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• Lazy Loading,Eager Loading,Explicit Loading in Entity Framework 4

  - by nikolaosk

  This is going to be the ninth post of a series of posts regarding ASP.Net and the Entity Framework and how we can use Entity Framework to access our datastore. You can find the first one here , the second one here , the third one here , the fourth one here , the fifth one here ,the sixth one here ,the seventh one here and the eighth one here . I have a post regarding ASP.Net and EntityDataSource . You can read it here .I have 3 more posts on Profiling Entity Framework applications. You can have a...(read more)

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• Execute TSQL statement with ExecuteStoreQuery in entity framework 4.0

  - by Jalpesh P. Vadgama

  I was playing with entity framework in recent days and I was searching something that how we can execute TSQL statement in entity framework. And I have found one great way to do that with entity framework ‘ExecuteStoreQuery’ method. It’s executes a TSQL statement against data source given enity framework context and returns strongly typed result. You can find more information about ExcuteStoreQuery from following link. http://msdn.microsoft.com/en-us/library/dd487208.aspx So let’s examine how it works. So Let’s first create a table against which we are going to execute TSQL statement. So I have added a SQL Express database as following. Now once we are done with adding a database let’s add a table called Client like following. Here you can see above Client table is very simple. There are only two fields ClientId and ClientName where ClientId is primary key and ClientName is field where we are going to store client name. Now it’s time to add some data to the table. So I have added some test data like following. Now it’s time to add entity framework model class. So right click project->Add new item and select ADO.NET entity model as following. After clicking on add button a wizard will start it will ask whether we need to create model classes from database or not but we already have our client table ready so I have selected generate from database as following. Once you process further in wizard it will be presented a screen where we can select the our table like following. Now once you click finish it will create model classes with for us. Now we need a gridview control where we need to display those data. So in Default.aspx page I have added a grid control like following. <%@ Page Title="Home Page" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="EntityFramework._Default" %> <asp:Content ID="HeaderContent" runat="server" ContentPlaceHolderID="HeadContent"> </asp:Content> <asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent"> <h2> Welcome to ASP.NET! </h2> <p> To learn more about ASP.NET visit <a href="http://www.asp.net" title="ASP.NET Website">www.asp.net</a>. </p> <p> You can also find <a href="http://go.microsoft.com/fwlink/?LinkID=152368&amp;clcid=0x409" title="MSDN ASP.NET Docs">documentation on ASP.NET at MSDN</a>. <asp:GridView ID="grdClient" runat="server"> </asp:GridView> </p> </asp:Content> Now once we are done with adding Gridview its time to write code for server side. So I have written following code in Page_load event of default.aspx page. protected void Page_Load(object sender, EventArgs e) { if (!Page.IsPostBack) { using (var context = new EntityFramework.TestEntities()) { ObjectResult<Client> result = context.ExecuteStoreQuery<Client>("Select * from Client"); grdClient.DataSource = result; grdClient.DataBind(); } } } Here in the above code you can see that I have written create a object of our entity model and then with the help of the ExecuteStoreQuery method I have execute a simple select TSQL statement which will return a object result. I have bind that object result with gridview to display data. So now we are done with coding.So let’s run application in browser. Following is output as expected. That’s it. Hope you like it. Stay tuned for more..Till then happy programming.

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• How to handle concurrency in Entity Framework

  - by nikolaosk

  This is going to be the fifth post of a series of posts regarding ASP.Net and the Entity Framework and how we can use Entity Framework to access our datastore. You can find the first one here , the second one here and the third one here . You can read the fourth one here . I have a post regarding ASP.Net and EntityDataSource. You can read it here .I have 3 more posts on Profiling Entity Framework applications. You can have a look at them here , here and here . In this post I will be looking into...(read more)

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• Identity Map Pattern and the Entity Framework

  - by nikolaosk

  This is going to be the seventh post of a series of posts regarding ASP.Net and the Entity Framework and how we can use Entity Framework to access our datastore. You can find the first one here , the second one here and the third one here , the fourth one here , the fifth one here and the sixth one here . I have a post regarding ASP.Net and EntityDataSource. You can read it here .I have 3 more posts on Profiling Entity Framework applications. You can have a look at them here , here and here . In...(read more)

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• Managing multiple references of the same game entity in different places using IDs

  - by vargonian

  I've seen great questions on similar topics, but none that addressed this particular method: Given that I have multiple collections of game entities in my [XNA Game Studio] game, with many entities belonging to multiple lists, I'm considering ways I could keep track of whenever an entity is destroyed and remove it from the lists it belongs to. A lot of potential methods seem sloppy/convoluted, but I'm reminded of a way I've seen before in which, instead of having multiple collections of game entities, you have collections of game entity IDs instead. These IDs map to game entities via a central "database" (perhaps just a hash table). So, whenever any bit of code wants to access a game entity's members, it first checks to see if it's even in the database still. If not, it can react accordingly. Is this a sound approach? It seems that it would eliminate many of the risks/hassles of storing multiple lists, with the tradeoff being the cost of the lookup every time you want to access an object.

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• Entity Framework DateTime update extremely slow

  - by Phyxion

  I have this situation currently with Entity Framework: using (TestEntities dataContext = DataContext) { UserSession session = dataContext.UserSessions.FirstOrDefault(userSession => userSession.Id == SessionId); if (session != null) { session.LastAvailableDate = DateTime.Now; dataContext.SaveChanges(); } } This is all working perfect, except for the fact that it is terribly slow compared to what I expect (14 calls per second, tested with 100 iterations). When I update this record manually through this command: dataContext.Database.ExecuteSqlCommand(String.Format("update UserSession set LastAvailableDate = '{0}' where Id = '{1}'", DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fffffff"), SessionId)); I get 55 calls per second, which is more than fast enough. However, when I don't update the session.LastAvailableDate but I update an integer (e.g. session.UserId) or string with Entity Framework, I get 50 calls per second, which is also more than fast enough. Only the datetime field is terrible slow. The difference of a factor 4 is unacceptable and I was wondering how I can improve this as I don't prefer using direct SQL when I can also use the Entity Framework. I'm using Entity Framework 4.3.1 (also tried 4.1).

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• Entity System with C++ templates

  - by tommaisey

  I've been getting interested in the Entity/Component style of game programming, and I've come up with a design in C++ which I'd like a critique of. I decided to go with a fairly pure Entity system, where entities are simply an ID number. Components are stored in a series of vectors - one for each Component type. However, I didn't want to have to add boilerplate code for every new Component type I added to the game. Nor did I want to use macros to do this, which frankly scare me. So I've come up with a system based on templates and type hinting. But there are some potential issues I'd like to check before I spend ages writing this (I'm a slow coder!) All Components derive from a Component base class. This base class has a protected constructor, that takes a string parameter. When you write a new derived Component class, you must initialise the base with the name of your new class in a string. When you first instantiate a new DerivedComponent, it adds the string to a static hashmap inside Component mapped to a unique integer id. When you subsequently instantiate more Components of the same type, no action is taken. The result (I think) should be a static hashmap with the name of each class derived from Component that you instantiate at least once, mapped to a unique id, which can by obtained with the static method Component::getTypeId ("DerivedComponent"). Phew. The next important part is TypedComponentList<typename PropertyType>. This is basically just a wrapper to an std::vector<typename PropertyType> with some useful methods. It also contains a hashmap of entity ID numbers to slots in the array so we can find Components by their entity owner. Crucially TypedComponentList<> is derived from the non-template class ComponentList. This allows me to maintain a list of pointers to ComponentList in my main ComponentManager, which actually point to TypedComponentLists with different template parameters (sneaky). The Component manager has template functions such as: template <typename ComponentType> void addProperty (ComponentType& component, int componentTypeId, int entityId) and: template <typename ComponentType> TypedComponentList<ComponentType>* getComponentList (int componentTypeId) which deal with casting from ComponentList to the correct TypedComponentList for you. So to get a list of a particular type of Component you call: TypedComponentList<MyComponent>* list = componentManager.getComponentList<MyComponent> (Component::getTypeId("MyComponent")); Which I'll admit looks pretty ugly. Bad points of the design: If a user of the code writes a new Component class but supplies the wrong string to the base constructor, the whole system will fail. Each time a new Component is instantiated, we must check a hashed string to see if that component type has bee instantiated before. Will probably generate a lot of assembly because of the extensive use of templates. I don't know how well the compiler will be able to minimise this. You could consider the whole system a bit complex - perhaps premature optimisation? But I want to use this code again and again, so I want it to be performant. Good points of the design: Components are stored in typed vectors but they can also be found by using their entity owner id as a hash. This means we can iterate them fast, and minimise cache misses, but also skip straight to the component we need if necessary. We can freely add Components of different types to the system without having to add and manage new Component vectors by hand. What do you think? Do the good points outweigh the bad?

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• Entity Framework 4 ste delete foreign key relationship

  - by user169867

  I'm using EF4 and STE w/ Silverlight. I'm having trouble deleting child records from my primary entity. For some reason I can remove child entities if their foreign key to my primary entity is part of their Primary Key. But if it's not, they don't get removed. I believe these posts explains it: http://mocella.blogspot.com/2010/01/entity-framework-v4-object-graph.html http://blogs.msdn.com/dsimmons/archive/2010/01/31/deleting-foreign-key-relationships-in-ef4.aspx My question is how how do I remove a child record who's foreign key is not part of its primary key in Silverlight where I don't have access to a DeleteObject() function?

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• Entity Relationship Model: Ternary Relationships

  - by Ethan

  Hi, I am trying to understand why this statement in the book is wrong: "given a C entity, there is at most one related A entity and at most one related B entity". Is it that it doesn't apply to a specific kind of relationship?? So, if I have an example of a student who is in attendance to a course with a type of subject. The entities are student, attendance, course and subject. Student makes attendance in a room. Also, a student can make attendance for a subject. Does this example apply to the statement? Thanks for your time.

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• ASP.Net Layered app - Share Entity Data Model amongst layers

  - by Chris Klepeis

  How can I share the auto-generated entity data model (generated object classes) amongst all layers of my C# web app whilst only granting query access in the data layer? This uses the typical 3 layer approach: data, business, presentation. My data layer returns an IEnumerable<T> to my business layer, but I cannot return type T to the presentation layer because I do not want the presentation layer to know of the existence of the data layer - which is where the entity framework auto-generated my classes. It was recommended to have a seperate layer with just the data model, but I'm unsure how to seperate the data model from the query functionality the entity framework provides.

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• Entity Framework How to specify paramter type in generated SQL (SQLServer 2005) Nvarchar vs Varchar

  - by Gratzy

  In entity framework I have an Entity 'Client' that was generated from a database. There is a property called 'Account' it is defined in the storage model as: <Property Name="Account" Type="char" Nullable="false" MaxLength="6" /> And in the Conceptual Model as: <Property Name="Account" Type="String" Nullable="false" /> When select statements are generated using a variable for Account i.e. where m.Account == myAccount... Entity Framework generates a paramaterized query with a paramater of type NVarchar(6). The problem is that the column in the table is data type of char(6). When this is executed there is a large performance hit because of the data type difference. Account is an index on the table and instead of using the index I believe an Index scan is done. Anyone know how to force EF to not use Unicode for the paramater and use Varchar(6) instead?

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• Entity framework : [Set all the entities with internal access specifier]

  - by Vedaantees

  Hi, By virtue of my application, I need to seperate my business entities from the entities created by EF4. I need to restrict the entities to only access the repository from where they are translated (using translator) to business entities shared at business and service layer. I thought of restricting them by specifying them as internal. Now there are more than 40 entities in my application so manually setting them as internal is a difficult job. In one of the forums the answers suggested using the T4 templates. But even those templates read from the entity framework access specifier. When I try to manually try to specify all the properties and class access specifiers as internal it gives me an error saying that the entity set should also be set to internal, but there is no option for the same. I am using VS 2010 and Entity Framework 4. Any suggestions???

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• Join with ADO.NET Linq to Entity in C#

  - by aladdin

  Hello I'm try to migrate a system to ADO.NET Entity I have 3 table A => (Id, Name, ...) B => (Id, Domain, ...) c => (IdA, IdB) VS.NET generate 2 entity A and B and both have reference to the other table but this reference is a collection. I need make a join between tables. from a in A join b in B on a.? equal b.? where condition select new { Name = a.Name, Domain = b.Domain }; I cant do that follow the reference in entity bu when the problem grows can be a problem. Any Help?

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• delete data using entity framework

  - by user3474542

  The objective of the method below is to delete the data from the database using entity framework. I am populating the subscriptions entity by passing two parameters and then calling the atttach and remove method of the context class. Bureau entities is the context class. using (BUREAUEntities bureauEntities = new BUREAUEntities()) { var subscription = new SubcriptionRepository().GetSusbcriptionBySubscriptionTypeId(subscriptionTypeId, companyId); bureauEntities.Subscriptions.Attach((DataAccessLayer.DatabaseModel.Subscription)subscription); bureauEntities.Subscriptions.Remove(subscription); bureauEntities.SaveChanges(); } I am getting the following error message at An entity object cannot be referenced by multiple instances of IEntityChangeTracker at line bureauEntities.Subscriptions.Attach((DataAccessLayer.DatabaseModel.Subscription)subscription); Could somebody tell me where am I going wrong ?

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• how to display the below xml in the flex datagrid

  - by Kishore

  <rows> - <row rowno="1"> - <row-value> <colno>1</colno> <value>1</value> </row-value> - <row-value> <colno>2</colno> <value>sel</value> </row-value> - <row-value> <colno>3</colno> <value>select * from qt_query</value> </row-value> - <row-value> <colno>4</colno> <value>kishore</value> </row-value> - <row-value> <colno>5</colno> <value>2009-04-10 00:00:00.0</value> </row-value> - <row-value> <colno>6</colno> </row-value> - <row-value> <colno>7</colno> </row-value> </row> - <row rowno="2"> - <row-value> <colno>1</colno> <value>2</value> </row-value> - <row-value> <colno>2</colno> <value>sel12345</value> </row-value> - <row-value> <colno>3</colno> <value>select * from qt_query</value> </row-value> - <row-value> <colno>4</colno> <value>kishore</value> </row-value> - <row-value> <colno>5</colno> <value>2009-04-10 00:00:00.0</value> </row-value> - <row-value> <colno>6</colno> <value>krajkumard</value> </row-value> - <row-value> <colno>7</colno> <value>2010-05-21 00:00:00.0</value> </row-value> </row> - <row rowno="3"> - <row-value> <colno>1</colno> <value>3</value> </row-value> - <row-value> <colno>2</colno> <value>sele123</value> </row-value> - <row-value> <colno>3</colno> - <value> select * from cache where %2scache_name% = ? and %1icache_type% = ? </value> </row-value> - <row-value> <colno>4</colno> <value>krajkumard</value> </row-value> - <row-value> <colno>5</colno> <value>2010-05-21 00:00:00.0</value> </row-value> - <row-value> <colno>6</colno> </row-value> - <row-value> <colno>7</colno> </row-value> </row> - <row rowno="4"> - <row-value> <colno>1</colno> <value>4</value> </row-value> - <row-value> <colno>2</colno> <value>upd</value> </row-value> - <row-value> <colno>3</colno> <value>select * from qt_qtool where %sname=?%</value> </row-value> - <row-value> <colno>4</colno> <value>krajkumard</value> </row-value> - <row-value> <colno>5</colno> <value>2010-05-31 00:00:00.0</value> </row-value> - <row-value> <colno>6</colno> </row-value> - <row-value> <colno>7</colno> <value>2010-06-07 00:00:00.0</value> </row-value> </row> - <row rowno="5"> - <row-value> <colno>1</colno> <value>5</value> </row-value> - <row-value> <colno>2</colno> <value>Pron_errors</value> </row-value> - <row-value> <colno>3</colno> <value>select * from proanalyzer_errors</value> </row-value> - <row-value> <colno>4</colno> <value>tjothy</value> </row-value> - <row-value> <colno>5</colno> <value>2010-06-07 00:00:00.0</value> </row-value> - <row-value> <colno>6</colno> </row-value> - <row-value> <colno>7</colno> </row-value> </row> </rows>

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• Using Entity Framework Table splitting customisations in an ASP.Net application

  - by nikolaosk

  I have been teaching in the past few weeks many people on how to use Entity Framework. I have decided to provide some of the samples I am using in my classes. First let’s try to define what EF is and why it is going to help us to create easily data-centric applications.Entity Framework is an object-relational mapping (ORM) framework for the .NET Framework.EF addresses the problem of Object-relational impedance mismatch . I will not be talking about that mismatch because it is well documented in many...(read more)

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