IsChild function Null safety
Determines whether a window is a child window or descendant window of a specified parent window. A child window is the direct descendant of a specified parent window if that parent window is in the chain of parent windows; the chain of parent windows leads from the original overlapped or pop-up window to the child window.
BOOL IsChild( HWND hWndParent, HWND hWnd );
int IsChild(int hWndParent, int hWnd) => _IsChild(hWndParent, hWnd);