I created a subclass of the ShapeNode class as follows:

               Public Class MyShapeNode
         Inherits ShapeNode
End Class

The reason I did this is because I want to add properties to the MyShapeNode class that the base class does not have.

To instantiate a MyShapeNode object I then wrote code like this:

Dim fnode As MyShapeNode = CType(dgmMain.Factory.CreateShapeNode(pt.X, pt.Y, 20, 20), MyShapeNode)

The text editor accepted the code, but when I ran the program, it threw an InvalidCastException. Maybe I need to go back to OOP school, but should this not work?

That did the trick. I wrote the following as a replacement for the Factory.CreateShapeNode method that accommodates subclasses:

               fnode = New MyShapeNode
               dgmMain.Nodes.Add(fnode)
               fnode.Bounds = New RectangleF(pt.X, pt.Y, 20, 20)

This way I can subsequently assign values to the subclass' properties.

Thanks again for the quick response.