title: Binding data to slider doesn't work
body: <p>I've got a problem with a binding in my windows phone project.  I'm binding an class to a slider, but it won't update the value.  If I first start the app, the binding connection is established correctly and the slider does have its correct value.  But if I change the "position" or "duration" value, the slider won't update with it.</p>
  
  <p>Can you please help me? I don't have any clue, what I'm doing wrong :(</p>
  
  <p>Class.cs:</p>
  
  <pre><code>public class Status : INotifyPropertyChanged
  {
    public event PropertyChangedEventHandler PropertyChanged;
    private void PropChanged(string propName)
    {
      if (PropertyChanged != null)
      {
        PropertyChanged(this, new PropertyChangedEventArgs(propName));
      }
    }
  
    public double duration
    {
      get { return _duration; }
      set
      {
        if (this._duration == value)
          return;
  
        _duration = value;
        PropChanged("duration");
      }
    }
  
    public double position
    {
      get { return _position; }
      set
      {
        if (this._position == value)
          return;
  
        _position = value;
        PropChanged("position");
      }
    }
  }
  </code></pre>
  
  <p>MainPage.xaml.cs:</p>
  
  <pre><code>public partial class MainPage : PhoneApplicationPage
  {
    public MainPage()
    {
      this.ContentPanel.DataContext = _Status;
    }
  }
  </code></pre>
  
  <p>MainPage.xaml:</p>
  
  <pre><code> ...
  &lt;Grid x:Name="ContentPanel" Margin="12,12,12,0" Grid.RowSpan="2"&gt;
      &lt;Slider x:Name="sl_PlayBackProgress"
              Value="{Binding Path=position}"
              Maximum="{Binding Path=duration}"
              Height="91"
              HorizontalAlignment="Left"
              Margin="0,40,0,0"
              VerticalAlignment="Top"
              Width="408"/&gt;
  &lt;/Grid&gt;
  ...
  </code></pre>