Here's my snippet.
I expected that this popup should be opened at the same position of mousepoint.
However, If I do not set the PlacementTarget property, it throws an exception (target null).
And, when I set the position, like above snippet, the position of popup changes time to time.
Moreover, I cannot understand why I should set the PlacementTarget property when I use "Placement=MousePoint".
How can I use this property?
Thank you in advance.