Determines which pop-up window owned by this window was most recently active. The return value is the same as the handle parameter, if any of the following conditions are met: 1) The window identified by hWnd was most recently active. 2) The window identified by hWnd does not own any pop-up windows. 3) The window identifies by hWnd is not a top-level window, or it is owned by another window.

public Win32Window LastActivePopup { get; }