Another problem

Using the nightly build from two days ago (because of the null reference bug) LightSpeed designer just deletes the model.cs it created, leaving only the .diagram file. I can see the model.cs file in the recycle bin. Of course i cannot access any domain objects...

 I should mention that this happens again and again so it's impossible to do any work.

 Switching nightly builds solved the issue.

Switching builds solved the issue.

I get the following SqlException:

"Cannot insert the value NULL into column 'Id', table '[...].Subject'; column does not allow nulls. INSERT fails.
The statement has been terminated."

My code is:

        static void Main(string[] args)
        {
            var context = new LightSpeedContext
                               {
                                   ConnectionString = "...",
                                   DataProvider = DataProvider.SqlServer2005,
                                   IdentityMethod = IdentityMethod.IdentityColumn
                               };

            using (var uow = context.CreateUnitOfWork())
            {
                uow.Add(new Subject() {Name = "name"});
                uow.SaveChanges();
            }
        }

Why is that?

With neither the entity nor the table definition it's hard to be sure, but I'm guessing that the Subject.Id column in the database is not an identity / autoincrement column.  You've specified the IdentityColumn identity method in your LightSpeedContext, so LightSpeed doesn't send an Id when you do a SaveChanges, expecting the database to supply one instead.

Note that the designer Update Database feature will never generate the Id column as identity / autoincrement.  If you're using model-first and IdentityColumn, you'll need to alter the table by hand.  (But if you're doing model-first you presumably have control over the database schema and should therefore not be using IdentityColumn anyway.)