Listview overflowing - not keeping size of parent?

Driving me crazy!

I have a Listview to which I am binding a large collection.

The problem is this collection "overflows" and then items can't be seen.

If I set Height- then fine, I开发者_如何学C get what I want and a scroll bar... but this won't dynamically size if the user maximises the entire window. So how can I tell it to fill the size of the groupbox it is in without overflowing and give me a scroll bar (vertical).

Sorry, A bit preemptive this question....

It was the stackpanel I had it in which was causing the problem.

Removed and set to a grid portion and is now working as needed.