Rectangles and Grids

Hey all,
I'm running into a weird issue with trying to get a rectangle to span an entire list item. Check out the screenshot attachment.

For the first list item there, I used the following XAML

Code:

---


<ListBoxItem HorizontalContentAlignment="Stretch">
. . .
<Rectangle Fill="Red" Grid.ColumnSpan="2" Grid.RowSpan="3" />
. . .

---

For the second, I'm using the C# code below

Code:

---

            Rectangle highlightRect = new Rectangle();
            Grid.SetColumnSpan(highlightRect, 2);
            Grid.SetRowSpan(highlightRect, 3);
            SolidColorBrush myBrush = new SolidColorBrush(Colors.Red);
            highlightRect.Fill = myBrush;

            . . .

            layoutGrid.Children.Add(highlightRect);

            . . .

            ListBoxItem theItem = new ListBoxItem();
            theItem.HorizontalContentAlignment = HorizontalAlignment.Stretch;
            theItem.Content = layoutGrid;

---

The first result, the one obtained from using that XAML, is the desired one. What am I not doing in the C# to make the rectangle fill up the rest of the space?

Thanks,
Lunchboxtheman

*smack*
In the XAML I had the width of the last column def to "*" and in the C# I had it set to "Auto".

I still don't understand the difference between the two, and where and when they can be applied. I'll have to read up more on that.

Thanks,
Lunchboxtheman

Auto means it will try to automatically size to the contents of the column, * means the columns will take up all available space :)