Linq to SQL Server CE and uniqueidentifier columns

There will be a couple of issues if you you try to use linq to sql with a SQL Server CE database. First of all the VS2008 designer doesn't allow adding tables from this type of database. The solution is to use the SqlMetal command line tool in order to generate the dbml or the code file (see here).

The second issue is that uniqueidentifier columns with the rowguid property will not work. More precisely, they will not autogenerate a value upon inserting a new row. Setting the column property to IsDbGenerated in the dbml mapping file is even worst: it will crash the insert operation. There is a workaround for this problem: in the partial class of the respective table entity, create the partial method "OnCreate" and manually set a new Guid for the new record:

partial void OnCreated()
{
    if (ID == Guid.Empty) ID = Guid.NewGuid();
}