My WPF Tiling Background Question on StackOverflow.com

I posted yet another difficult-to-answer question on stackoverflow.com. My question is not difficult because it is “advanced” or “smart” in any way. I’m forced to ask this question because of some not-so-brilliant design choices made for me—and one I made myself:

• A UserControl of variable height is hosted in another control—it is marked with Visibility = Hidden by default.
• I made this UserControl taller by appending a block to it.
• When I temporarily mark it as Visible and look at it in Expression Blend I can see the misalignment problem—had I looked at this last week I would not have posted my question on StackOverflow.com.It seems like the problem is related to this possible constraint/rule about WPF: a tiled background will try to fit itself within the given dimensions without regard for Visibility.Collapsed. I know I’m not explaining this very well but… oh, well…

The bottom line (for me) is that I need a design that allows me to “drop down” a panel that is independent of the height of its container. I’m looking for a drop-down container.

rasx()