Question

I’m getting some strange behaviour from EF Code First when I add an object to the database and select it back from the database in the same HTTP request.

When I retrieve it, it is returned as the object type rather than of type System.Data.Entity.DynamicProxies so the lazy loading doesn’t work.

If I retrieve the same object in the next HTTP Request then it is return as type System.Data.Entity.DynamicProxies and the lazy loading works fine.

Do I need to do something to the object or the context to get a DynamicProxy returned? Or is this how EF Code First is meant to work, if so how do I get around this issue?

I’ve even recreated the problem using the sample code in the NuGet packages.

Here’s the code that I used to recreate the problem:

public ActionResult Index() {
    var blogContext = new BlogContext();

    var posts = blogContext.Posts;

    ViewBag.Message = "Welcome to ASP.NET MVC!";
    ViewBag.Posts = posts;

    return View();
}

public ActionResult AddPost() {
    var blogContext = new BlogContext();

    var post = new Post() {
        PublishDate = DateTime.Now,
        Text = "Text",
        Title = "Title",
    };

    blogContext.Posts.Add( post );

    blogContext.SaveChanges();

    var post2 = blogContext.Posts.Find( post.ID );

    return RedirectToAction( "Index" );
}

public ActionResult GetPost(int id) {
    var blogContext = new BlogContext();

    var post = blogContext.Posts.Find( id );

    ViewBag.Post = post;

    return View();
}

When I get post2 in the AddPost action it is return of type MvcApplication.Models.Post where as when I return the same post in the GetPost action it is of type System.Data.Entity.DynamicProxies.Post.

The above code was recreated using the default MVC3 Application from the MVC 3 Tools Update I also installed the following NuGet packages: EntityFramework.Sample and EntityFramework.SqlServerCompact.

If anyone can recreate the problem or has a solution for this then it would be greatly appreciated.

Answer 1

In C#, if you call new Post(), then you’re going to get a Post instance, not an instance of a proxy subtype of Post. To get a proxy, you have to call something different.

You can, e.g., call DbSet<T>.Create:

var post = blogContext.Posts.Create();
post.PublishDate = DateTime.Now;