Binding WP7 Maps control to ViewModel, Problem with MapMode

Question

I am trying to reproduce the BingMaps sample of the Windows Phone 7 trainingkit: http://msdn.microsoft.com/en-us/wp7trainingcourse_usingbingmapslab_topic2.aspx#_Toc271039352

but instead of wiring everything in codebehind i'd like to use a viewmodel.

Everything works fine except binding to the Mode property (aerial or road) causes a XamlParseException. Is there a problem because it isn't a simple property?

This is the original Xaml:

            <my:Map Name="Map"
                    CredentialsProvider="{Binding CredentialsProvider}">
                 <my:Map.Mode>
                    <my:AerialMode ShouldDisplayLabels="True" />
                </my:Map.Mode>
            </my:Map>

The Map.Mode can be changed from codebehind.

Instead I am trying the following:

        <my:Map x:Name="Map"
                CredentialsProvider="{Binding CredentialsProvider}"
                ZoomLevel="{Binding Zoom, Mode=TwoWay}"
                Center="{Binding Center, Mode=TwoWay}"
                Mode="{Binding MapMode}" />

and the important part of the viewmodel:

    private MapMode _mapMode = new AerialMode(true);
    public MapMode MapMode
    {
        get { return _mapMode; }
        set
        {
            _mapMode = value;
            RaisePropertyChanged("MapMode");
        }
    }

    private void ChangeMapMode()
    {
        if (MapMode is AerialMode)
        {
            MapMode = new RoadMode();
        }
        else
        {
            MapMode = new AerialMode(true);
        }
    }

Thanks for your help!

Answer 1

Solved.

"Mode" isn't a dependency property. So it cannot be bound.

My workaround:

• added dependency property to view (=Page)
• bound dependency property to property in viewmodel (via code in the constructor)

• Set Mode of Map control in the propertyChanged callback handler

  //Constructor
  public MainPage()
  {
      InitializeComponent();
      DataContext = new MainViewModel();
      Binding b = new Binding("MapMode");
      this.SetBinding(MapModeProperty, b);
  }
  
  
  //DependencyProperty. No need for corresponding CLR-property.
  public static readonly DependencyProperty MapModeProperty =
      DependencyProperty.Register("MapMode", typeof(MapMode), typeof(MainPage), 
      new PropertyMetadata(OnMapModeChanged));
  
  
  //Callback
  private static void OnMapModeChanged(DependencyObject element,
         DependencyPropertyChangedEventArgs e)
  {
      ((MainPage)element).Map.Mode = e.NewValue as MapMode;
  }
  

Hope this one will help others!

Answer 2

I suspect you'll need to use a converter with your binding.