title: designer shows A 'Binding' can only be set on a DependencyProperty of a DependencyObject error
body: <p>I've created a user control that has a DependencyProperty, and when I try binding to it I get an error in the designer: </p>
  
  <blockquote>
    <p>" 'Binding' cannot be set on the 'ROCValue' property of type
    'RocIndicator'. A 'Binding' can only be set on a DependencyProperty of
    a DependencyObject.</p>
  </blockquote>
  
  <p><strong>Edit:</strong> I've added the static modifier, but I still get that error. and yes, I've restarted visual studio.</p>
  
  <pre><code>public partial class RocIndicator : UserControl
  {
      public static readonly DependencyProperty ROCValueProperty =
          DependencyProperty.Register("ROCValue", typeof(double), typeof(RocIndicator),
          new FrameworkPropertyMetadata(0.0, new PropertyChangedCallback(ValueChanged)));
  
  
      public double ROCValue
      {
          get { return (double)GetValue(ROCValueProperty); }
          set { SetValue(ROCValueProperty, value); }
      }
  }
  </code></pre>
  
  <p>this is the XAML:</p>
  
  <pre><code>&lt;View:RocIndicator ROCValue="{Binding ROC}" Margin="0,10,0,0" HorizontalAlignment="Center" Width="35"/&gt;
  </code></pre>
  
  <p>but when I build &amp; run it works. why is this error showing?</p>