在呈现之前确定SizeToContent WPF窗口的大小

I have a window in my WPF application that is displayed on occasion. When it is shown it is faded in with an annimation, and when closed it is faded out. Nothing fancy, just a storyboard that modifies the opacity. Actually the window is never really closed, the opacity is just faded out to 0 where it remains until its to be displayed again.I have a window in my WPF application that is d