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:

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

Remove the primary key like so

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

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