I've got a Silverlight user control that contains a datagrid. The datagrid is bound to an ObservableCollection. The user control is displayed in a popup window that I show in response to some event in another control
There are about 80 objects in the collection, and I've set a fixed height of 400 on the datagrid, so only about 20 items can be shown at one time, and the vertical scrollbar should be shown, with a thumb size occupying about 1/4th of the control height.
However, what's actually happening is that the scrollbar occupies almost the whole control height; maybe 95% of it. The datagrid displays the first 20 items. When I click on the scrollbar down arrow, the scrollbar moves down a little to occupy the bottom 95% of the scroll area, and the datagrid displays the last 20 items.
It gets weirder. If I move over the items in the grid and scroll down using the mouse wheel, then the items scroll correctly and I can view the whole list, although the scrollbar remains the same size.
And then, if I close the popup and reopen it, the scrollbar now appears with the correct height and it works correctly.
Finally, if I just show the control directly on the page, and not in a popup, it works fine. What's going on here?! Has anyone else run into this problem? Help!
Update: The problem seems to be the way that I'm showing the popup. For various reasons, I had to implement the popup display in a somewhat tricky way, and it's this that's causing the trouble.
