Thank you XAML guy - that worked. I thought I had background in there, seems missed it.
What I really want is to have a border line formatting with Brush, something like this:
<LinearGradientBrush StartPoint="0,0" EndPoint="0,1.0"><GradientStop Color="#FFCF4118" Offset="0.0" /><GradientStop Color="#FFEE5326" Offset="1.0" /></LinearGradientBrush>
But when I apply this to the Border it's applied throughout the border space, in other words the upper line of the border is different to the lower etc. I would like to be applied to the line itself. I've tried to format the Line first and use that within the Border, but it didn't work. Is this possible ?