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To understand what VBDT's class is doing (in a much simpler example) scan down the page towards the bottom to find the following which gives a simple example of the way to use the Region/Graphics Path:

Next Steps
In the example above that used an instance of the GraphicsPath class, you specified a string, which was then used to determine the primary shape of the control. However, you may wish to have controls that are not text-shaped, but rather geometrically shaped (such as a triangle or circle). The .NET Framework includes provisions for this as well.

Rather than specifying a string to render as the shape of the button, you can use shapes that have been predefined within the .NET Framework. Using these shapes in combination allows you a great degree of control over the look of your controls.