title: WPF: Border.BorderThickness=0 doesn't work
body: <p>I have the following xaml:</p>
  
  <pre><code>&lt;UserControl x:Class="MyCompany.MyApp.MySubModule.Views.MyView"
               xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
               xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
               xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
               xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
               mc:Ignorable="d" 
               d:DesignHeight="43" d:DesignWidth="115"&gt;
      &lt;Grid&gt;
          &lt;Border Margin="20, 0, 0, 0" CornerRadius="0, 10, 10, 0" BorderBrush="Transparent" BorderThickness="0"&gt;
              &lt;Border.Background&gt;
                  &lt;LinearGradientBrush StartPoint="0,0" EndPoint="1,0"&gt;
                      &lt;GradientStopCollection&gt;
                          &lt;GradientStop Color="#0066CC" Offset="0" /&gt;
                          &lt;GradientStop Color="#0075EA" Offset="1" /&gt;
                      &lt;/GradientStopCollection&gt;
                  &lt;/LinearGradientBrush&gt;
              &lt;/Border.Background&gt;
          &lt;/Border&gt;
      &lt;/Grid&gt;
  &lt;/UserControl&gt;
  </code></pre>
  
  <p>What I'd expect is that the <code>Border</code> would have no thickness (i.e. not be visible). But in fact you can see it. Why would that be, and how do I make it go away?</p>