In Silverlight, let's say I have a <Border VerticalAlignment="Top"/> with some contents in it. Now those contents change and become bigger; the Border automatically resizes of course to accomodate the new content. So far so good.

 

But what if I want to animate that change? So when the content of the <Border> control changes, I want it to animate from its current size to the new size. Note that I cannot predict what the size of the new content will be, so I can't just hard-code a value in an animation.

 

I can't find any way to do this. Any ideas?