Visual Studio Lightswitch v2 issue

If you import a datasource with a table named Systems, it will not complain until compile time, when it says "no such object System.CodeDom...". Basically it is a name collision.

"Can not insert NULL into column" when SaveChanges in Entity Framework

It is a strange error as the value is obviously set in the POCO used. The reason is the model created marked the column as 'Identity', which causes EF to insert a NULL and try to get the value back from database. If you use SQL Profiler, you can see the behavior clearly.

How to autosize font size for a textblock in Xaml?

Use <ViewBox> around it.