Question

I apologize for the newbie question, but I am struggling with this problem. I have the following TextBlock defined:

<TextBlock Text='{Binding Source={x:Static local:DeviceManager.Instance},  Path=Player.CurrentArtist}'></TextBlock> 

The DeviceManager is a singleton that functions as a facade for other classes. For example, Player is a property of type IPlayer which represents an music-playing application. I would like the TextBlock to display the artist that is currently playing, which is periodically updated in the Player.CurrentArtist property.

Unfortunately, I cannot get the TextBlock to update when the CurrentArtist property updates. Both the DeviceManager and the IPlayer implement INotifyPropertyChanged, but when I step through the application, the DeviceManager does not have an event handler attached to it.

Does anyone have a suggestion for how to update the text block while preserving the singleton-facade?

Here is the code for the INotifyPropertyChanged members in both the DeviceManager and the IPlayer subclass:

public sealed class DeviceManager : INotifyPropertyChanged {     // Singleton members omitted      public IPlayer Player     {         get { return player; }         set         {             this.player = value;             player.PropertyChanged += new PropertyChangedEventHandler(device_PropertyChanged);         }     }      #region INotifyPropertyChanged Members      public event PropertyChangedEventHandler PropertyChanged;      private void device_PropertyChanged(object sender, PropertyChangedEventArgs e)     {         PropertyChangedEventHandler handler = PropertyChanged;         if (handler != null)         {             handler(sender, e);         }     }      #endregion }  class MediaPlayer : IPlayer {     private string artist;     private string title;      public event PropertyChangedEventHandler PropertyChanged;      public void Play(string artist, string title)     {         this.artist = artist;         this.title = title;         OnPropertyChanged('Player:Song');     }      private void OnPropertyChanged(string p)     {         PropertyChangedEventHandler handler = PropertyChanged;         if (handler != null)         {             handler(this, new PropertyChangedEventArgs(p));         }     }      public string CurrentTitle     {         get { return title; }     }      public string CurrentArtist     {         get { return artist; }     }  } 

Answer 1

The problem is that WPF is never notified of the value of the CurrentArtist property changing. You can either implement a private setter for the CurrentArtist property, which will trigger the PropertyChanged event, or trigger a PropertyChanged event for the CurrentArtist property in MediaPlayer.Play().