title: Mask all elements of a window/canvas with C#/WPF
body: <p>How can I create a mask to cover ALL the elements of a Windows/Canvas (with subcanvas/elements inside)?</p>
  
  <p>Thanks in advance</p>
  
  <p>EDIT: I want to add more controls/elements/whatever <strong>after</strong> I create the mask. Is that ok? How?</p>