title: Fallback or default value for Content binding to ValueConverter
body: <p>I have a content control that shows dynamic content based on the current state. This all works fine but, for design time, i'd like it to show the default state.  Is there any way I can do this using either the <code>ValueConverter</code> or <code>FallbackValue</code> or something?</p>
  
  <p>XAML</p>
  
  <pre><code>&lt;ContentControl Content="{Binding State, 
                Converter={StaticResource InstallationStateToControlConverter}}" /&gt;
  </code></pre>
  
  <p>C#</p>
  
  <pre><code>class InstallationStateToControlConverter : IValueConverter
  {
      public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
      {            
          //return controls depending on the state
          switch ((InstallationState)value)
          {
              case InstallationState.LicenceAgreement:
                  return new LicenceAgreementControl();
              default:
                  return new AnotherControl();
          }
      }
  
      public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
      {
          throw new NotImplementedException();
      }
  }
  </code></pre>
  
  <p><strong>Update</strong></p>
  
  <p>As per Viv's question I have added the following to my XAML, it compiles ok but I still see nothing in the designer?</p>
  
  <pre><code>d:DataContext="{d:DesignInstance Type=local:LicenceAgreementControl, IsDesignTimeCreatable=True}"
  </code></pre>