wpf - Draw all the Non-Client area in C#

Question

I am looking to draw my non-client area in C#, for example, instead a rectangle as a form, i want an ellipse (this is an example), but how can i do it?

I basically want to draw all my non client area, and i think to do that i will have to override some methods, but which ones?

I have found an example that uses 'xaml', what i think that is windows presentation foundation app, but i haven't understand it well.

Answer 1

m0sa has provided a WPF answer already.

For WinForms, you'll need to process the WM_NCPAINT message (override Control.WndProc) and also enable the layered window style in order to have transparent regions in the bounding box.