Trying to use Entity Framework with asp.net MVC3

Question

I'm trying to make EntityFramework work with ASP .NET MVC3 using this tutorial:

http://www.asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-an-entity-framework-data-model-for-an-asp-net-mvc-application

Ok, I have my database, my .edmx model, model classes but one first thing I don't get is: How does my DbContext derived class even know my .emdx model ? I don't fine where the "link" is created in this tutorial (maybe having several thing with the same name "SchoolContext", for the context as for the connexionstring is confusing ...)

When I run what I got for now with the code:

    MMContext context = new MMContext();

    List<EntityUser> testList = (from u in context.Users
                                select u).ToList();

I get:

System.Data.Edm.EdmEntityType: : EntityType 'EntityUser' has no key defined. Define the key for this EntityType.

System.Data.Edm.EdmEntitySet: EntityType: EntitySet �Users� is based on type �EntityUser� that has no keys defined.

Thank you for your help.

But this tutorial shows Code-First approach. You should not have an EDMX file at all. Or are you trying to "convert" the example to Database- or Model-First? — Slauma
Sorry, I'm actually looking for a Database first approx (well, I mean I created the model based on an existing DB). A good tutorial for that would help me. — TTT
Brief DB & Model First introduction (for EF >= 4.1) is here: blogs.msdn.com/b/adonet/archive/2011/09/28/… — Slauma
I've just tried this but the ".tt" entries have no icons which looks weird dans their ".cs" files are just empty. — TTT

Marc Marc · Accepted Answer · 2012-04-05T17:22:23

Assuming you are using the Code-First approach, you have to define a Key in your Users class:

public class User
{
    public int Id { get; set; }
    // ...
}

As mentioned from Kyle, if your ID field is not named "Id" you have to add the [Key] attribute:

using System.ComponentModel.DataAnnotations;
public class User
{
    [Key]
    public int u_Id { get; set; }
    // ...
}

Trying to use Entity Framework with asp.net MVC3

1 Answers