How to support NULLs in XSD?

[Bob]

I've added an XSD to my VB.NET solution and created the schema in the
designer. The Oracle table allows nulls. I used the XSD.EXE to create the
..VB file for the dataset. When I try to load the dataset I get an error
unless I edit the .VB file for the dataset and change the allownulls to TRUE.
Is there a way to set these without having to open the .VB file and edit it?