Windows Transparency

A great article on the new features of the the Windows Presentation Foundation (WPF) can be found on MSDN. Many of the following quotes are taken from that article.

"GDI+ offers partial transparency and anti-aliasing for drawing operations, but only when performed within the confines of a single control." - MSDN

"With Win32, and the associated GDI and GDI+ drawing APIs, each control in the UI owns its part of the window exclusively. Windows are carved up by the controls into a set of disjointed regions that are usually, but not necessarily, rectangular. If you pick any single pixel on a window, there will be exactly one control responsible for drawing that pixel." - MSDN

"WPF breaks free from this limitation. No single control or UI element has exclusive ownership of any part of the window in a WPF application. You can create partially transparent UI elements, or controls that are not visually constrained to their logical rectangle. For example, it's possible for a control to cast a shadow that falls outside of its logical region." - MSDN

"In effect, the whole window becomes a single drawing surface that each of the parts of the UI contribute to." - MSDN