Is there a way to get entity id-field's name by reflection or whatever?

Question

I am trying to get the ID field name (property name) of an entity, is it possible?

User user= new User(); //User is an Entity

string idField = ??????? //user.UserId

Answer 1

If you can get the EntitySet, or the EntityType, for the entity, then you can use the KeyMembers property:

public IEnumerable<string> GetIdProperties(EntitySetBase entitySet)
{
  return GetIdProperties(entitySet.ElementType);
}

public IEnumerable<string> GetIdProperties(EntityTypeBase entityType)
{
  return from keyMember in entityType.KeyMembers
         select keyMember.Name
}

You can obtain a generic object set from the context:

public ObjectSet<TEntity> GetEntitySet<TEntity>(ObjectContext context)
{
    return context.CreateObjectSet<TEntity>();
}