/// <summary>
 /// Subscribes the provided handler for update notifications.
 /// </summary>
 /// <param name="handler">The update notification handler.</param>
 public void Subscribe(IFabricServiceStatusListener handler)
 {
     this.subscribers.TryAdd(handler, handler);
 }
 /// <summary>
 /// Unsubscribes the provided handler from update notifications.
 /// </summary>
 /// <param name="handler">The update notification handler.</param>
 public void Unsubscribe(IFabricServiceStatusListener handler)
 {
     this.subscribers.TryRemove(handler, out handler);
 }
 public void Unsubscribe(IFabricServiceStatusListener handler)
 {
     this.Handlers.Remove(handler);
 }