If it is transparent, it's not really black. :-)
If you think what is transparency, you will understand that this concept is a kind of metaphor. It only makes sense if you have something to show under a "transparent" graphics. Moreover, it has strict sense only if there is some motion. You move top object and observe the objects underneath. You need to think if you want a form to be transparent, and see the windows of the different applications under it.
That said, you should understand that transparency of control is not well supported by
. If you need something flexible and advanced, switch to WPF, don't waste time of Forms, or give it up. If you have something limited, think about rendering of GDI objects in one custom control; this will work perfectly. And of course, don't even think about using
; it makes no sense at all. Please see some of my past answers:How do I clear a panel from old drawing
],draw a rectangle in C#
],Append a picture within picturebox
see also:Drawing Lines between mdi child forms
],capture the drawing on a panel
],What kind of playful method is Paint? (DataGridViewImageCell.Paint(...))
],How to speed up my vb.net application?