silverlight、C#，为 XAML 添加额外控制

Question

As many bing maps silverlight developers already know, bing maps contains a method called setview that calculates the right zoomlevel for the map.

I myself built a map applicion with an MVVM framework. I want to use the setview method also for my map. But because i built the app in an MVVM, it won't be good to use setview in the viewmodel, because the viewmodel doesn't know anything about the map.xaml

I have an XAML with the map UI. I connected the XAML to a viewmodel, called mapcontent.cs.

In the viewmodel called, mapcontent.cs, i have a property like this:

 public LocationRect MapArea {
  get { return new LocationRect(new Location(52.716610, 6.921160), new Location(52.718330, 6.925840)); }
}

Now i want to use the setview, but this with the MVVM set up. So i created an extra control of the Map class:

namespace Markarian.ViewModels.Silverlight.Controls {
  /// <summary>
  /// Map control class
  /// </summary>
  public class Map: MC.Map {
    /// <summary>
    /// Initializes a new instance of the Map class.
    /// </summary>
    public Map() {

    }

    /// <summary>
    /// gets and sets setview.
    /// </summary>
    public MC.LocationRect ViewArea { get; set; } <<<setview will come here
  }
}

now the solution will be, that i can use ViewArea in my XAML and bind that with MapArea. The only problem is that i can't use the property Viewarea in XAML, does anyone know why?

Answer 1

Your ViewArea property would have to be a DependencyProperty in order to support bindings. What you have is a plain old CLR property.

To hook up the SetView call, you'd have to add a change handler to your dependency property. This article has an example/explaination, but it would be like:

public MC.LocationRect ViewArea {
    get { return (MC.LocationRect)GetValue(ViewAreaProperty); }
    set { SetValue(ViewAreaProperty, value); }
}

public static readonly DependencyProperty ViewAreaProperty = DependencyProperty.Register("ViewArea", typeof(MC.LocationRect),
    typeof(Map), new PropertyMetadata(new MC.LocationRect(), OnViewAreaChanged));

private static void OnViewAreaChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) {
    var map = d as Map;
    // Call SetView here
}