Solution to the "You tried to assign the Null value to a variable that is not a Variant data type." Exception

By default the DataSource wizard passes parameters for AutoNumber primary keys. If you are getting this error: You tried to assign the Null value to a variable that is not a Variant data type.

Then you need to remove that default parameter.

This is what Visual Studio adds by default:

InsertCommand="INSERT INTO [Partner] ([PartnerId], [PartnerGuid], [Name]) VALUES (?, ?, ?)"

Remove the primary key like so

InsertCommand="INSERT INTO [Partner] ([PartnerGuid], [Name]) VALUES (?, ?)"