Window.Left and Window.Top
var location = myTextBlock.PointToScreen(new Point(0, 0));
window.Left = location.X;
window.Top = location.Y - window.Height;
Window.Left and Window.Top
var location = myTextBlock.PointToScreen(new Point(0, 0));
window.Left = location.X;
window.Top = location.Y - window.Height;