Element is already the child of another


I would like to report two troubles.
If I call the next lines:
then everything is well. But if I write the next:
it may cause an error in your source code on the next line:
// If no closing storyboard is defined, close the Popup
this.ChildWindowPopup.IsOpen = false;
because ChildWindowPopup is not initialized yet.
Now, when I try the next snippet:
// some little delay
// some little delay
_aboutView.Show(); // line 3 !
sometimes on line 3 get an exception: <Element is already the child of another>
it happens, I guess, because this.ParentLayoutRoot.Children still contains a FloatableWindow instance. It removes it only when sb.Completed occurs, but my little_delay sometimes it too little for your animation to be completed in time. So, when the line
is called the ParentLayoutRoot still has it.