Localization of a WPF application using a custom MarkupExtension

 
 <TextBlock Text="{l:Translate CustomerForm.FirstName}" />
 
 

 
public class TranslateExtension : MarkupExtension
{
    private string _key;
 
    public TranslateExtension(string key)
    {
        _key = key;
    }
 
    [ConstructorArgument("key")]
    public string Key
    {
        get { return _key; }
        set { _key = value;}
    }
 
    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        var binding = new Binding("Value")
              {
                  Source = new TranslationData(_key)
              };
        return binding.ProvideValue(serviceProvider);
    }
}
 
 

 
public class TranslationData : IWeakEventListener, 
                  INotifyPropertyChanged
{
    private string _key;
 
    public TranslationData( string key)
    {
        _key = key;
        LanguageChangedEventManager.AddListener(
                  TranslationManager.Instance, this);
    }
 
    ~TranslationData()
    {
        LanguageChangedEventManager.RemoveListener(
                 TranslationManager.Instance, this);
    }
 
    public object Value
    {
        get
        {
            return TranslationManager.Instance.Translate(_key);
        }
    }
 
    public bool ReceiveWeakEvent(Type managerType, 
                            object sender, EventArgs e)
    {
        if (managerType == typeof(LanguageChangedEventManager))
        {
            OnLanguageChanged(sender, e);
            return true;
        }
        return false;
    }
 
    private void OnLanguageChanged(object sender, EventArgs e)
    {
        if( PropertyChanged != null )
        {
            PropertyChanged( this, new PropertyChangedEventArgs("Value"));
        }
    }
 
    public event PropertyChangedEventHandler PropertyChanged;
}
 
 

 
public class TranslationManager
{
    private static TranslationManager _translationManager;
 
    public event EventHandler LanguageChanged;
 
    public CultureInfo CurrentLanguage
    {
        get { return Thread.CurrentThread.CurrentUICulture; }
        set
        {
           if( value != Thread.CurrentThread.CurrentUICulture)
           {
               Thread.CurrentThread.CurrentUICulture = value;
               OnLanguageChanged();
           }
        }
    }
 
   public IEnumerable<CultureInfo> Languages
   {
       get
       {
           if( TranslationProvider != null)
           {
               return TranslationProvider.Languages;
           }
           return Enumerable.Empty<CultureInfo>();
       }
    }
 
    public static TranslationManager Instance
    {
        get
        {
            if (_translationManager == null)
                _translationManager = new TranslationManager();
            return _translationManager;
        }
    }
 
    public ITranslationProvider TranslationProvider { get; set; }
 
   private void OnLanguageChanged()
   {
        if (LanguageChanged != null)
        {
            LanguageChanged(this, EventArgs.Empty);
       }
    }
 
   public object Translate(string key)
   {
       if( TranslationProvider!= null)
       {
            object translatedValue =TranslationProvider.Translate(key);
            if( translatedValue != null)
           {
               return translatedValue;
           }
        }
       return string.Format("!{0}!", key);
    }
}