/// <summary>
 ///
 /// </summary>
 /// <typeparam name="TData"></typeparam>
 /// <param name="bus"></param>
 /// <param name="handler">处理器</param>
 public static void Unsubscribe <TData>(this IMessageBus bus, Action <TData> handler)
 {
     Guard.NotNull(bus, "bus");
     Guard.NotNull(handler, "handler");
     bus.Unsubscribe(null, typeof(TData), ObserverHandler.Create1 <TData>(handler));
 }