In Entity Framework, getting the value of an identity column after inserting

Question

I'm using EF4. I want to insert a new MyObject into the database. MyObject has two fields:

Id: int (Identity) and Name: string

As I've seen in documentation Entity Framework is supposed to set MyObject.Id to the value generated by database after the call to SaveChanges() but in my case that doesn't happen.

using (var context = new MyEntities())
{
    var myObject = MyObjects.CreateMyObject(0, "something"); // The first parameter is identity "Id"
    context.MyObjects.AddObject(myObject);
    context.SaveChanges();
    return myObject.Id; // The returned value is 0
}

UPDATE:

This happens in one of my entities and others work fine. By the way, I checked and the DB column is identity and StoreGeneratedPattern is set to Identity. Here is the SSDL. I don't see any difference. The first one isn't working right:

    <EntityType Name="OrgUnit">
      <Key>
        <PropertyRef Name="Srl" />
      </Key>
      <Property Name="Srl" Type="int" Nullable="false" StoreGeneratedPattern="Identity" />
      <Property Name="TypeId" Type="smallint" Nullable="false" />
      <Property Name="Name" Type="varchar" Nullable="false" MaxLength="80" />      
    </EntityType>

    <EntityType Name="OrgType">
      <Key>
        <PropertyRef Name="Srl" />
      </Key>
      <Property Name="Srl" Type="smallint" Nullable="false" StoreGeneratedPattern="Identity" />
      <Property Name="Title" Type="varchar" Nullable="false" MaxLength="120" />
      <Property Name="Options" Type="int" Nullable="false" />
    </EntityType>

The update is done successfully in the database and the identity is generated but the entity object is not updated with the new identity.

Answer 1

If you are using Linq To Entities, and get this error even if you followed the advices of marc_s (that are really good), you should look at your entites directly in the edmx (xml view) and check if they have the following attribute :

    <EntityType Name="MyEntity">
      <Key>
        <PropertyRef Name="pk" />
      </Key>
      <Property Name="pk" Type="bigint" Nullable="false" StoreGeneratedPattern="Identity" />
      <Property Name="value" Type="float" Nullable="false" />
    </EntityType>

The StoreGeneratedPattern="Identity" is also required.