Question

Paraphrasing from this MSDN documentation …

An INSERT statement is generated by
the Entity Framework and executed on
the data source when SaveChanges is
called on the ObjectContext.

If the INSERT operation succeeds,
server-generated values are written
back to the ObjectStateEntry. When
AcceptChanges is called automatically
at the end of the SaveChanges
execution, a permanent EntityKey is
computed by using the new
server-generated values.

This does not seem to be occurring in my code. When I call ObjectContext.SaveChanges(), an UpdateException is thrown with InnerException.Message value:

“duplicate key value violates unique constraint student_term_data_pkey”

Here is the offending code:

using (DataAccessLayerEntities context = new DataAccessLayerEntities()) {
     StudentTermData mostCurrent = new StudentTermData() {
          // Foreign keys:    
          StudentId = studentId,
          TermId = currentTerm.Id,

          // Non-nullable properties:
          SponsorCode = string.Empty,
          AdmissionNumber = string.Empty,
          Expiration = string.Empty
     };

     context.StudentTermDatas.AddObject(mostCurrent);
     context.SaveChanges();  // UpdateException occurs here.
}

I have verified that StudentTermData.Id is marked as an EntityKey in my Entity data model. Does anyone have any ideas or suggestions?

Answer 1

This problem was caused by a bug in EF4 where the EF designer doesn’t set the StoreGeneratedPattern attribute in the SSDL. The problem is documented in this blog and this Microsoft Connect ticket.

The solution was to open my model’s .edml file in a text editor, locate the <EntityType Name="student_term_data"> XML tag, and add StoreGeneratedPattern="Identity" to the property tag being used as an EntityKey:

  <EntityType Name="student_term_data">
     <Key><PropertyRef Name="id" /></Key>
     <Property Name="id" Type="int" Nullable="false" StoreGeneratedPattern="Identity" />
     ...
  </EntityType>

I then re-opened my model in the EF designer, made a small change (moved an entity position) and saved. This caused the code generator to run, presumably synchronizing the CDSL with the SSDL.

My code now runs as expected.