title: Entity Framework CTP 4. "Cannot insert the value NULL into column" - Even though there is no NULL value
body: <p>Im using EF CTP 4. I have a simple console app (for testing purposes) that is using EF to insert some data into a SQL database.</p>
  
  <p>I have come to a problem where by upon inserting the item </p>
  
  <pre><code>using(var context = GetContext())
  {
     BOB b = new BOB();
     b.Id = 1;
  
     context.Bobs.Add(b);
     context.SaveChanges();
  }
  </code></pre>
  
  <p>It throws the error: <em>{"Cannot insert the value NULL into column 'Id', table 'TestDB.dbo.BOB'; column does not allow nulls. INSERT fails.\r\nThe statement has been terminated."}</em></p>
  
  <p>The Table just has 1 field of <em>Id int NOT NULL</em> which is the primary key and is <strong>not</strong> an auto incremented Id.</p>
  
  <p>On the creation of the DataContext I have this configuration, which yes does get fired.</p>
  
  <pre><code>protected override void OnModelCreating(ModelBuilder builder)
  {
      builder.Entity&lt;BOB&gt;().HasKey(b =&gt; b.Id);
      builder.Entity&lt;BOB&gt;().MapSingleType().ToTable("BOB");
  }
  </code></pre>
  
  <p>I have also pre-populated this table and then through the debugger been able to via <em>watch</em> load up this BOB object... so I am really stumped, as for being able to load up my BOB shows that all is right... however upon inserting a new one it crashes...</p>