<p>Apparantly when users right-click in our WPF application, and they use the Windows Classic theme, the default ContextMenu of the TextBox (which contains Copy, Cut and Paste) has a black background.</p>

<p>I know this works well:</p>

<pre><code>&lt;Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"&gt;

  &lt;TextBox ContextMenu="{x:Null}"/&gt;

&lt;/Page&gt;
</code></pre>

<p>But this doesn't work:</p>

<pre><code>&lt;Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"&gt;

&lt;Page.Resources&gt;

 &lt;Style x:Key="{x:Type TextBox}" TargetType="{x:Type TextBox}"&gt;
   &lt;Setter Property="ContextMenu" Value="{x:Null}"/&gt;
&lt;/Style&gt;
&lt;/Page.Resources&gt;

  &lt;TextBox/&gt;
&lt;/Page&gt; 
</code></pre>

<p>Does anyone know how to style or disable the default ContextMenu for all TextBoxes in WPF?</p>

Try removing the x:Key attribute from the Style resource, leaving TargetType.  I know, you're supposed to have that x:Key for a resource, but if you have it along with your TargetType the Key prevails.
Here's a sample style that I use in a project to skin all tooltips in one of my apps (this is in App.Resources--notice, no Key)
```
```
<Style
    TargetType="{x:Type ToolTip}">
    <Setter
      Property="Template">
      <Setter.Value>
        <ControlTemplate
          TargetType="{x:Type ToolTip}">
          <Grid
            Width="{TemplateBinding Width}"
            Height="{TemplateBinding Height}">
            <Rectangle
              RadiusX="9"
              RadiusY="9"
              Stroke="LightGray"
              StrokeThickness="2">
              <Rectangle.Fill>
                <RadialGradientBrush>
                  <GradientStop />
                  <GradientStop
                    Color="FloralWhite"
                    Offset="0" />
                  <GradientStop
                    Color="Cornsilk"
                    Offset="2" />
                </RadialGradientBrush>
              </Rectangle.Fill>
            </Rectangle>
            <ContentPresenter
              Margin="6 4 6 4" />
          </Grid>
        </ControlTemplate>
      </Setter.Value>
    </Setter>
  </Style>
```
```