Remove a StackPanel / Grid Unwanted Default Border?

I'm designing a UI in Visual Studio 2010, and I've come across a slight problem. I'm fairly new to XAML and this method of design, so this might be a rookie mistake. I've looked around but can't seem to find reference to a similar problem.

Basically, I have a grid with 2 rows, one of which contains开发者_运维问答 a stackpanel and 5 columns. The stackpanel sits behind the columns and is used to paint the background of the entire row. When I add a background colour to the other row, I get an annoying line at the top of the stackpanel which just looks out of place. I've tried several things (showGridLines = false, transparent borders etc) but cannot seem to get rid of it. The best way to show it is through an image:

See http://img227.imageshack.us/img227/2220/tempym.jpg

One oddity I've noticed is that when I resize the window, at certain points the line disappears. Obviously this is not a solution (not least because it's going to be run full screen), but adds to the mystery of the line...

This is a trivial problem, but it is annoying me and will continue to do so until I can get rid of it, so any help would be appreciated. I've omitted the xaml for simplicity, but will post if required.

Based on the oddity you noticed, try setting SnapsToDevicePixels to true on the grid or window. Sounds like the borders are falling in between pixel boundaries and is being anti-aliased.

Or rather, if you're using .NET 4.0, use UseLayoutRounding instead.