title: Bing Maps route poly line can not be removed from map
body: <p>I have the following xaml to bind an instance of the class <code>LocationCollection</code> to an instance of the class <code>MapPolyline</code>.</p>
  
  <pre><code> &lt;Microsoft_Phone_Controls_Maps:MapPolyline Stroke="Green"
                                              Locations="{Binding Points}"
                                              StrokeThickness="6"
                                              Opacity="0.7" /&gt;
  </code></pre>
  
  <p>The <code>Points</code> property is defined in the ViewModel as:</p>
  
  <pre><code>public LocationCollection Points
  {
      get
      {
          return this.points;
      }
      set
      {
          this.SetPropertyAndNotify(ref this.points, value, "Points");
      }
  }
  </code></pre>
  
  <p>Now when I set the <code>Points</code> property the route line is displayed as expected but when I want to remove the line with the following code the line is still displayed - even though I've created a new empty <code>LocationCollection</code> class and notify the property has changed.</p>
  
  <p>Anyone got any idea why the route line is not removed?</p>
  
  <pre><code>this.Points = new LocationCollection();
  </code></pre>