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  • HUGE EF4 Inheritance Bug

    - by djsolid
    Well maybe not for everyone but for me is definitely really important. That is why I get straight into the point. We have the following model: Which maps to the following database: We are using EF4.0 and we want to load all Burgers including BurgerDetails. So we write the following query: But it fails. The error is : “The ResultType of the specified expression is not compatible with the required type. The expression ResultType is 'Transient.reference[SampleEFDBModel.Food]' but the required type is 'Transient.reference[SampleEFDBModel.Burger]'.Parameter name: arguments[0]”   So in the new version of EF there is no way to eager load data through Navigation Properties with 1-1 relationships defined in subclasses. Here is the relevant Microsoft Connect Issue. It is described through an other example but the result is the same.  Please if you think this is important vote up on Microsoft Connect.   EF 4.0 has many improvements. I am using it since v1 in large-scale projects and this version is faster,produces cleaner sql, more reliable and can be used for complicated business scenarios. That is why I believe this issue should be solved as soon as possible. I understand that release cycles are slow but I am hoping atleast for a hotfix. I also have uploaded the example project so you can test it. Download it from here. If anyone has found any workarounds please post it in the comments section. Thanks!

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  • Not loading the object caused EF4 (code first) to remove the relationship

    - by Lavinski
    Firstly this is a EF4: Code First - Property Loading question. I'm loading an object like so var item = Context.Table.Find( update.Identifier ); This object has a property Relationship so a table has a Relationship object. Now i'm updating my item but my Relationship object is not toched (and therefore not lazy loaded). Now here's the problem .. I save my item and my relationship to the Relationship object is deleted, apparently the model thinks i set it to null. However it all works if I look at the property before saving. So I'm looking into LoadProperty or doing a query and using Include. Has anyone else come across this issue and how did you get around it?

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  • EF4 performance tips and tricks

    - by Will
    I've gotten to that point in one of my projects, and haven't found much information out there. So if you've got some pointers for improving performance in the new Entity Framework 4, please let us know!

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  • EF4, MVC 3, Azure and Code First or Traditional

    - by RichardAlanA
    I am planning to build a web application using ASP MVC3 that runs on Azure with a SQL Azure back end. I would like to use the Microsoft stack and have no plans to ever change to another stack. I am looking into the use of WCF and WF but that would be in the future. I looked at the traditional and Code First approach to using Entity Framework but I can't see if there is any advantage in using one or the other approach. Sure they each have advantages but for me I don't care if my classes do inherit from EF classes. All I want is to find the most efficient solution. Can anyone out there give me some advice as to which approach might be the best. thanks very much Richard

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  • Fix for EF4 Profiler Issue Coming in next Cumulative Update

    - by Ajarn Mark Caldwell
    Hey!  What do you know?  Microsoft Connect really works! I was very happy this morning to open my email and find a notice from Umachandar on the SQL Programmability Team that they have created a fix for the Odd Profiler Results with EF4 issue that I wrote about last June.  Not only did I blog about it, but I logged an item to Connect with repro steps and sample code.  And now, they have announced that they have a fix for this problem and that it will be included in the next Cumulative Update for SQL Server 2008 R2. For those of you not running 2008 R2, or who prefer to wait for full Service Packs rather than install the latest Cumulative Updates, I also wrote about a workaround for the issue, as long as you do not require the Multiple Active Result Sets feature to be enabled. It is easy with Microsoft to get the feeling that you’re just shouting in the wind, and it is nice to get validation once in a while that they really are listening.

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  • Hard Core EF4 Full-Day Workshop, June 23rd, Stockholm

     The date (June 23rd), the city (Stockholm) and the abstract are firm. Now I have to wait for the person organizing this workshop on my behalf to provide registration details. This will be a public workshop. I will update this blog post, write a new one and also tweet (twitter.com/julielerman) the details as soon as I have them. Hard Core EF4 Full Day of Advanced Entity Framework 4 Workshop with Julie Lerman You’ve been working...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • EF4 CPT5 Code First Remove Cascading Deletes

    - by Dane Morgridge
    I have been using EF4 CTP5 with code first and I really like the new code.  One issue I was having however, was cascading deletes is on by default.  This may come as a surprise as using Entity Framework with anything but code first, this is not the case.  I ran into an exception with some one-to-many relationships I had: Introducing FOREIGN KEY constraint 'ProjectAuthorization_UserProfile' on table 'ProjectAuthorizations' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints. Could not create constraint. See previous errors. To get around this, you can use the fluent API and put some code in the OnModelCreating: 1: protected override void OnModelCreating(System.Data.Entity.ModelConfiguration.ModelBuilder modelBuilder) 2: { 3: modelBuilder.Entity<UserProfile>() 4: .HasMany(u => u.ProjectAuthorizations) 5: .WithRequired(a => a.UserProfile) 6: .WillCascadeOnDelete(false); 7: } This will work to remove the cascading delete, but I have to use the fluent API and it has to be done for every one-to-many relationship that causes the problem. I am personally not a fan of cascading deletes in general (for several reasons) and I’m not a huge fan of fluent APIs.  However, there is a way to do this without using the fluent API.  You can in the OnModelCreating, remove the convention that creates the cascading deletes altogether. 1: protected override void OnModelCreating(System.Data.Entity.ModelConfiguration.ModelBuilder modelBuilder) 2: { 3: modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>(); 4: } Thanks to Jeff Derstadt from Microsoft for the info on removing the convention all together.  There is a way to build a custom attribute to remove it on a case by case basis and I’ll have a post on how to do this in the near future.

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  • Odd Profiler Results with EF4

    - by AjarnMark
    I have been doing some testing of using the Microsoft Entity Framework 4 with stored procedures and ran across some really odd results in SQL Server Profiler. The application that is running which uses Entity Framework 4 is a simple Web Application written in C#, and the Entity Data Model is actually contained in a referenced class library of its own.  I’ll write more about my experiences with this later.  For now the question is, why does SQL Profiler think that the stored procedure is running in Master, and not in my application database? While analyzing the effects of using custom helper methods on my EDM classes to call the stored procedure, I decided to run Profiler while I stepped through the code so that I had a clear understanding of exactly when and what calls were made to the SQL Server.  I ran Profiler switching back and forth between the TSQL and TSQL_SP templates.  However, to reduce the amount of results rows I needed to wade through, I set a filter on DatabaseID to be equal to my application’s database.  Each time I ran this, the only thing that I saw was an Audit:Login to the database, but no procedure or T-SQL statements executed, yet I was definitely getting results back to my web page.  I tried other Profiler templates, still filtering on DatabaseID (tangent: I found, at least back in SQL 2000 Profiler, that filtering on DatabaseID was more reliable than filtering on DatabaseName.  Even though I’m now running SQL 2008, that habit sticks with me).  Still no results other than the Login.  Very weird! Finally, I decided to run Profiler with no filtering and discovered that that lines which represent my stored procedure and its T-SQL commands are all marked with DatabaseID = 1, which is Master.  Why in the world would that be?  My procedure is definitely in the application database, and not in Master, and there is nothing funny about the call to the procedure evident in Profiler (i.e. it is not called as MyAppDB.dbo.MyProcName, but rather just dbo.MyProcName).  There must be something funny with the way the Entity Framework is wrapping this call, and I don’t like it…I don’t like it one bit.  My primary PROD server contains 40+ databases on it, and when I need to profile something, I expect to be able to filter based on DatabaseID (for the record, I displayed DatabaseName in my results, too, and it also shows Master). I find the same pattern of everything except the Login showing up as being in Master when I run my version that uses standard LINQ to Entities instead of stored procedures, so that suggests it is not my code, but rather something funny with SQL Server 2008 Profiler or the Entity Framework. If you have any ideas about why this might be so, please comment below.

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  • EF4 Code First Control Unicode and Decimal Precision, Scale with Attributes

    - by Dane Morgridge
    There are several attributes available when using code first with the Entity Framework 4 CTP5 Code First option.  When working with strings you can use [MaxLength(length)] to control the length and [Required] will work on all properties.  But there are a few things missing. By default all string will be created using unicode so you will get nvarchar instead of varchar.  You can change this using the fluent API or you can create an attribute to make the change.  If you have a lot of properties, the attribute will be much easier and require less code. You will need to add two classes to your project to create the attribute itself: 1: public class UnicodeAttribute : Attribute 2: { 3: bool _isUnicode; 4:  5: public UnicodeAttribute(bool isUnicode) 6: { 7: _isUnicode = isUnicode; 8: } 9:  10: public bool IsUnicode { get { return _isUnicode; } } 11: } 12:  13: public class UnicodeAttributeConvention : AttributeConfigurationConvention<PropertyInfo, StringPropertyConfiguration, UnicodeAttribute> 14: { 15: public override void Apply(PropertyInfo memberInfo, StringPropertyConfiguration configuration, UnicodeAttribute attribute) 16: { 17: configuration.IsUnicode = attribute.IsUnicode; 18: } 19: } The UnicodeAttribue class gives you a [Unicode] attribute that you can use on your properties and the UnicodeAttributeConvention will tell EF how to handle the attribute. You will need to add a line to the OnModelCreating method inside your context for EF to recognize the attribute: 1: protected override void OnModelCreating(System.Data.Entity.ModelConfiguration.ModelBuilder modelBuilder) 2: { 3: modelBuilder.Conventions.Add(new UnicodeAttributeConvention()); 4: base.OnModelCreating(modelBuilder); 5: } Once you have this done, you can use the attribute in your classes to make sure that you get database types of varchar instead of nvarchar: 1: [Unicode(false)] 2: public string Name { get; set; }   Another option that is missing is the ability to set the precision and scale on a decimal.  By default decimals get created as (18,0).  If you need decimals to be something like (9,2) then you can once again use the fluent API or create a custom attribute.  As with the unicode attribute, you will need to add two classes to your project: 1: public class DecimalPrecisionAttribute : Attribute 2: { 3: int _precision; 4: private int _scale; 5:  6: public DecimalPrecisionAttribute(int precision, int scale) 7: { 8: _precision = precision; 9: _scale = scale; 10: } 11:  12: public int Precision { get { return _precision; } } 13: public int Scale { get { return _scale; } } 14: } 15:  16: public class DecimalPrecisionAttributeConvention : AttributeConfigurationConvention<PropertyInfo, DecimalPropertyConfiguration, DecimalPrecisionAttribute> 17: { 18: public override void Apply(PropertyInfo memberInfo, DecimalPropertyConfiguration configuration, DecimalPrecisionAttribute attribute) 19: { 20: configuration.Precision = Convert.ToByte(attribute.Precision); 21: configuration.Scale = Convert.ToByte(attribute.Scale); 22:  23: } 24: } Add your line to the OnModelCreating: 1: protected override void OnModelCreating(System.Data.Entity.ModelConfiguration.ModelBuilder modelBuilder) 2: { 3: modelBuilder.Conventions.Add(new UnicodeAttributeConvention()); 4: modelBuilder.Conventions.Add(new DecimalPrecisionAttributeConvention()); 5: base.OnModelCreating(modelBuilder); 6: } Now you can use the following on your properties: 1: [DecimalPrecision(9,2)] 2: public decimal Cost { get; set; } Both these options use the same concepts so if there are other attributes that you want to use, you can create them quite simply.  The key to it all is the PropertyConfiguration classes.   If there is a class for the datatype, then you should be able to write an attribute to set almost everything you need.  You could also create a single attribute to encapsulate all of the possible string combinations instead of having multiple attributes on each property. All in all, I am loving code first and having attributes to control database generation instead of using the fluent API is huge and saves me a great deal of time.

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  • Winnipeg Code Camp EF4 Resources

    - by Aaron Kowall
    I had fun presenting “What’s new in Entity Framework 4” at the Winnipeg Code Camp today. I mentioned some resources on my deck that I thought I’d include here in my blog. •EF 4.0 Hands on Labs •EF CTP  5 (has the new DbContext and CodeFirst support)   •MSDN Data Developer Center: MSDN.com/Data •ADO.NET Team Blog •EF Design Blog •How to choose an inheritance strategy Programming Entity Framework, Second Edition by Julia Lerman

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  • Programming Entity Framework, 2nd Edition (EF4) Table of Contents

    We are closing in on finalizing the 2nd edition of Programming Entity Framework! Although the rough draft chapters are already available through Safari’s Rough Cuts program (here: http://oreilly.com/catalog/9780596807252) I have been editing and reshaping the content since those chapters were published. You can get the final print edition (August 15th or perhaps a bit earlier) at O’Reilly or pre-order it here on Amazon.com (here) (and elsewhere of course!) I believe that the book will...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Extending EF4 SQL Generation

    - by Basiclife
    Hi, We're using EF4 in a fairly large system and occasionally run into problems due to EF4 being unable to convert certain expressions into SQL. At present, we either need to do some fancy footwork (DB/Code) or just accept the performance hit and allow the query to be executed in-memory. Needless to say neither of these is ideal and the hacks we've sometimes had to use reduce readability / maintainability. What we would ideally like is a way to extend the SQL generation capabilities of the EF4 SQL provider. Obviously there are some things like .Net method calls which will always have to be client-side but some functionality like date comparisons (eg Group by weeks in Linq to Entities ) should be do-able. I've Googled but perhaps I'm using the wrong terminology as all I get is information about the new features of EF4 SQL Generation. For such a flexible and extensible framework, I'd be surprised if this isn't possible. In my head, I'm imagining inheriting from the [SQL 2008] provider and extending it to handle additional expressions / similar in the expression tree it's given to convert to SQL. Any help/pointers appreciated. We're using VS2010 Ultimate, .Net 4 (non-client profile) and EF4. The app is in ASP.Net and is running in a 64-Bit environment in case it makes a difference.

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  • What's the easiest way to sort an EF4 EntityCollection<T>?

    - by Will
    I'd love to add some sorting to an EntityCollection that is bound to an ItemsControl (in xaml). I'd also like to do it as simply as possible. It appears that this is not possible. If I wrap the collection in a "sorted" version of the collection property within the Entity I lose collection change notifications. I can't use a CollectionViewSource because the entity collection's BindingListCollectionView does not support sorting for some goddamned reason (note: I've seen the blog post with the "dirty" hack to get around this, so please don't answer with that kthx). Is there a simple (couple lines of xaml, couple lines of code, whatever) way to achieve this??

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  • EF4 cross database relationships

    - by Daniel
    Hello all, I was wondering if EF4 support cross-databse relationships? For instance: db1 Author Id Name db2 Posts Id Content db1.Author.Id What ideally I need to do to get this relation in my ef4 model? Do you guys have any idea? Thanks

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  • EF4 Code First - Many to many relationship issue

    - by Yngve B. Nilsen
    Hi! I'm having some trouble with my EF Code First model when saving a relation to a many to many relationship. My Models: public class Event { public int Id { get; set; } public string Name { get; set; } public virtual ICollection<Tag> Tags { get; set; } } public class Tag { public int Id { get; set; } public string Name { get; set; } public virtual ICollection<Event> Events { get; set; } } In my controller, I map one or many TagViewModels into type of Tag, and send it down to my servicelayer for persistence. At this time by inspecting the entities the Tag has both Id and Name (The Id is a hidden field, and the name is a textbox in my view) The problem occurs when I now try to add the Tag to the Event. Let's take the following scenario: The Event is already in my database, and let's say it already has the related tags C#, ASP.NET If I now send the following list of tags to the servicelayer: ID Name 1 C# 2 ASP.NET 3 EF4 and add them by first fetching the Event from the DB, so that I have an actual Event from my DbContext, then I simply do myEvent.Tags.Add to add the tags.. Problem is that after SaveChanges() my DB now contains this set of tags: ID Name 1 C# 2 ASP.NET 3 EF4 4 C# 5 ASP.NET This, even though my Tags that I save has it's ID set when I save it (although I didn't fetch it from the DB)

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  • EF4 Code-First CTP5 Many-to-one

    - by Kevin McKelvin
    I've been trying to get EF4 CTP5 to play nice with an existing database, but struggling with some basic mapping issues. I have two model classes so far: public class Job { [Key, Column(Order = 0)] public int JobNumber { get; set; } [Key, Column(Order = 1)] public int VersionNumber { get; set; } public virtual User OwnedBy { get; set; } } and [Table("Usernames")] public class User { [Key] public string Username { get; set; } public string EmailAddress { get; set; } public bool IsAdministrator { get; set; } } And I have my DbContext class exposing those as IDbSet I can query my users, but as soon as I added the OwnedBy field to the Job class I began getting this error in all my tests for the Jobs: Invalid column name 'UserUsername'. I want this to behave like NHibernate's many-to-one, whereas I think EF4 is treating it as a complex type. How should this be done?

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  • Customize the SimpleMembership in ASP.NET MVC 4.0

    - by thangchung
    As we know, .NET 4.5 have come up to us, and come along with a lot of new interesting features as well. Visual Studio 2012 was also introduced some days ago. They made us feel very happy with cool improvement along with us. Performance when loading code editor is very good at the moment (immediate after click on the solution). I explore some of cool features at these days. Some of them like Json.NET integrated in ASP.NET MVC 4.0, improvement on asynchronous action, new lightweight theme on Visual Studio, supporting very good on mobile development, improvement on authentication… I reviewed them, and found out that in this version of .NET Microsoft was not only developed new feature that suggest from community but also focused on improvement performance of existing features or components. Besides that, they also opened source more projects, like Entity Framework, Reactive Extensions, ASP.NET Web Stack… At the moment, I feel Microsoft want to open source more and more their projects. Today, I am going to dive in deep on new SimpleMembership model. It is really good because in this security model, Microsoft actually focus on development needs. As we know, in the past, they introduce some of provider supplied for coding security like MembershipProvider, RoleProvider… I don’t need to talk but everyone that have ever used it know that they were actually hard to use, and not easy to maintain and unit testing. Why? Because every time you inherit it, you need to override all methods inside it. Some people try to abstract it by introduce more method with virtual keyword, and try to implement basic behavior, so in the subclass we only need to override the method that need for their business. But to me, it’s only the way to work around. ASP.NET team and Web Matrix knew about it, so they built the new features based on existing components on .NET framework. And one of component that comes to us is SimpleMembership and SimpleRole. They implemented the Façade pattern on the top of those, and called it is WebSecurity. In the web, we can call WebSecurity anywhere we want, and make a call to inside wrapper of it. I read a lot of them on web blog, on technical news, on MSDN as well. Matthew Osborn had an excellent article about it at his blog. Jon Galloway had an article like this at here. He analyzed why old membership provider not fixed well to ASP.NET MVC and how to get over it. Those are very good to me. It introduced to me about how to doing SimpleMembership on it, how to doing it on new ASP.NET MVC web application. But one thing, those didn’t tell me was how to doing it on existing security model (that mean we already had Users and Roles on legacy system, and how we can integrate it to this system), that’s a reason I will introduce it today. I have spent couples of hours to see what’s inside this, and try to make one example to clarify my concern. And it’s lucky that I can make it working well.The first thing, we need to create new ASP.NET MVC application on Visual Studio 2012. We need to choose Internet type for this web application. ASP.NET MVC actually creates all needs components for the basic membership and basic role. The cool feature is DoNetOpenAuth come along with it that means we can log-in using facebook, twitter or Windows Live if you want. But it’s only for LocalDb, so we need to change it to fix with existing database model on SQL Server. The next step we have to make SimpleMembership can understand which database we use and show it which column need to point to for the ID and UserName. I really like this feature because SimpleMembership on need to know about the ID and UserName, and they don’t care about rest of it. I assume that we have an existing database model like So we will point it in code like The codes for it, we put on InitializeSimpleMembershipAttribute like [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]     public sealed class InitializeSimpleMembershipAttribute : ActionFilterAttribute     {         private static SimpleMembershipInitializer _initializer;         private static object _initializerLock = new object();         private static bool _isInitialized;         public override void OnActionExecuting(ActionExecutingContext filterContext)         {             // Ensure ASP.NET Simple Membership is initialized only once per app start             LazyInitializer.EnsureInitialized(ref _initializer, ref _isInitialized, ref _initializerLock);         }         private class SimpleMembershipInitializer         {             public SimpleMembershipInitializer()             {                 try                 {                     WebSecurity.InitializeDatabaseConnection("DefaultDb", "User", "Id", "UserName", autoCreateTables: true);                 }                 catch (Exception ex)                 {                     throw new InvalidOperationException("The ASP.NET Simple Membership database could not be initialized. For more information, please see http://go.microsoft.com/fwlink/?LinkId=256588", ex);                 }             }         }     }And decorating it in the AccountController as below [Authorize]     [InitializeSimpleMembership]     public class AccountController : ControllerIn this case, assuming that we need to override the ValidateUser to point this to existing User database table, and validate it. We have to add one more class like public class CustomAdminMembershipProvider : SimpleMembershipProvider     {         // TODO: will do a better way         private const string SELECT_ALL_USER_SCRIPT = "select * from [dbo].[User]private where UserName = '{0}'";         private readonly IEncrypting _encryptor;         private readonly SimpleSecurityContext _simpleSecurityContext;         public CustomAdminMembershipProvider(SimpleSecurityContext simpleSecurityContext)             : this(new Encryptor(), new SimpleSecurityContext("DefaultDb"))         {         }         public CustomAdminMembershipProvider(IEncrypting encryptor, SimpleSecurityContext simpleSecurityContext)         {             _encryptor = encryptor;             _simpleSecurityContext = simpleSecurityContext;         }         public override bool ValidateUser(string username, string password)         {             if (string.IsNullOrEmpty(username))             {                 throw new ArgumentException("Argument cannot be null or empty", "username");             }             if (string.IsNullOrEmpty(password))             {                 throw new ArgumentException("Argument cannot be null or empty", "password");             }             var hash = _encryptor.Encode(password);             using (_simpleSecurityContext)             {                 var users =                     _simpleSecurityContext.Users.SqlQuery(                         string.Format(SELECT_ALL_USER_SCRIPT, username));                 if (users == null && !users.Any())                 {                     return false;                 }                 return users.FirstOrDefault().Password == hash;             }         }     }SimpleSecurityDataContext at here public class SimpleSecurityContext : DbContext     {         public DbSet<User> Users { get; set; }         public SimpleSecurityContext(string connStringName) :             base(connStringName)         {             this.Configuration.LazyLoadingEnabled = true;             this.Configuration.ProxyCreationEnabled = false;         }         protected override void OnModelCreating(DbModelBuilder modelBuilder)         {             base.OnModelCreating(modelBuilder);                          modelBuilder.Configurations.Add(new UserMapping());         }     }And Mapping for User as below public class UserMapping : EntityMappingBase<User>     {         public UserMapping()         {             this.Property(x => x.UserName);             this.Property(x => x.DisplayName);             this.Property(x => x.Password);             this.Property(x => x.Email);             this.ToTable("User");         }     }One important thing, you need to modify the web.config to point to our customize SimpleMembership <membership defaultProvider="AdminMemberProvider" userIsOnlineTimeWindow="15">       <providers>         <clear/>         <add name="AdminMemberProvider" type="CIK.News.Web.Infras.Security.CustomAdminMembershipProvider, CIK.News.Web.Infras" />       </providers>     </membership>     <roleManager enabled="false">       <providers>         <clear />         <add name="AdminRoleProvider" type="CIK.News.Web.Infras.Security.AdminRoleProvider, CIK.News.Web.Infras" />       </providers>     </roleManager>The good thing at here is we don’t need to modify the code on AccountController. We only need to modify on SimpleMembership and Simple Role (if need). Now build all solutions, run it. We should see a screen like thisIf I login to Twitter button at the bottom of this page, we will be transfer to twitter authentication pageYou have to waiting for a moment Afterwards it will transfer you back to your admin screenYou can find all source codes at my MSDN code. I will really happy if you guys feel free to put some comments as below. It will be helpful to improvement my code in the future. Thank for all your readings. 

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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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  • Where I can find SQL Generated by Entity framework?

    - by Jalpesh P. Vadgama
    Few days back I was optimizing the performance with Entity framework and Linq queries and I was using LinqPad and looking SQL generated by the Linq or entity framework queries. After some point of time I got the same question in mind that how I can find the SQL Statement generated by Entity framework?. After some struggling I have managed to found the way of finding SQL Statement so I thought it would be a great idea to write a post about  same and share my knowledge about that. So in this post I will explain how to find SQL statements generated Entity framework queries. Read More on dotnetjalps.com

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  • Association not imported in EF4 designer for non-primary key

    - by Rommel Manalo
    The relationship 'FK_EXTERNAL_ISMARKETI_MARKETIN' has columns that are not part of the key of the table on the primary side of the relationship. The relationship was excluded. USE [Instruments.UnitTest] GO ALTER TABLE [Instr].[ExternalIdentification] WITH CHECK ADD CONSTRAINT [FK_EXTERNAL_ISMARKETI_MARKETIN] FOREIGN KEY([InstrumentID], [MarketInstrumentID]) REFERENCES [Instr].[MarketInstrument] ([InstrumentID], [MarketInstrumentID]) GO ALTER TABLE [Instr].[ExternalIdentification] CHECK CONSTRAINT [FK_EXTERNAL_ISMARKETI_MARKETIN] GO I'm using an association for NON-PRIMARY KEY columns, is this possible in the EF4?

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  • Need help converting SQL to EF4 please

    - by Ken Eldridge
    I need help converting this SQL statement, into EF4: Select Posts.PostID, Post, Comment from Posts left join Comments on posts.PostID = Comments.PostID Where CommentID not in ( Select PostID from Votes where VoteTypeID = 4 --4 = flagged comment type ) In my database, the Votes table stores either the PostID of reported posts, or CommentID of reported comments in the column Votes.PostID Thanks in advance!

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  • Custom Validation with MVC2 and EF4

    - by csharpnoob
    Hi, on ScottGu's Blog is an Example how to use MVC2 Custom Validation with EF4: http://weblogs.asp.net/scottgu/archive/2010/01/15/asp-net-mvc-2-model-validation.aspx So here the Problem: When the Designer in VS2010 creates the Objects for the DB, along to the example you have to add [MetadataType(typeof(Person_validation))] Annotation to that class. But when i change anything in the Designer all these Annotations are lost. Is it possible to keep self made changes to the edmx file, or is there any better way of applying System.ComponentModel.DataAnnotations to the generated Entities? Thanks.

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