title: Visual appearance is not updated for UWP custom control in VS designer
body: <p>I have a Windows 10 UWP custom control that is deployed as an extension SDK.<br/>
  The control's generic.xaml looks like this:</p>
  
  <pre><code>&lt;Style TargetType="local:PdfDocumentView" &gt;
      &lt;Setter Property="Template"&gt;
          &lt;Setter.Value&gt;
              &lt;ControlTemplate TargetType="local:PdfDocumentView"&gt;
                  &lt;ScrollViewer x:Name="PdfScroller" HorizontalScrollBarVisibility="Auto" HorizontalScrollMode="Auto" VerticalScrollBarVisibility="Auto" VerticalScrollMode="Auto"
                      Background="{TemplateBinding Background}"
                      BorderBrush="{TemplateBinding BorderBrush}"
                      BorderThickness="{TemplateBinding BorderThickness}"&gt;
                      &lt;local:PdfCoreView x:Name="PdfPageView" Background="{TemplateBinding Background}" /&gt;
                  &lt;/ScrollViewer&gt;
              &lt;/ControlTemplate&gt;
          &lt;/Setter.Value&gt;
      &lt;/Setter&gt;
  &lt;/Style&gt;
  </code></pre>
  
  <p>The layout of the extension SDK looks like this:<br/>
  Redist\CommonConfiguration\neutral\Themes\generic.xaml<br/>
  Redist\CommonConfiguration\neutral\Xfinium.Pdf.View.Uwp.pri<br/>
  References\CommonConfiguration\neutral\xfinium.pdf.uwp.dll
  References\CommonConfiguration\neutral\xfinium.pdf.render.uwp.dll
  References\CommonConfiguration\neutral\xfinium.pdf.view.uwp.dll</p>
  
  <p>There are no architecture specific folders as the control is pure .NET compiled using AnyCPU option.<br/>
  At design time I drag the PdfDocumentView control from the toolbox on the page and set the Background, BorderBrush and BorderThickness properties.</p>
  
  <p>If the active platform is set to x86, the control appearance is updated in the designer according to the above 3 properties. If the active platform is changed to x64 or ARM the control becomes transparent, as if none of the above properties is set. </p>
  
  <p>At runtime the control is displayed ok, all 3 properties are considered, no matter the platform, x86 or x64.</p>
  
  <p>What could be the problem with the VS designer and the x64 platform?</p>