异步的两种写法: async 与 BeginInvoke

现在要实现异步只要用关键字async/await就可以轻松实现,在此之前需要用到委托/回调等一堆东西。

对一下是对比写法：

   class Program
     {
         delegate string SendMessage(string msg);
         static void Main(string[] args)
         {
             SendMessage sm = new SendMessage(DoAction);
             sm.BeginInvoke("asyn asyn asyn ... ...", new AsyncCallback(CallBack), null);

             DoAsync("async keywod.. ...");

             Console.WriteLine("do do do .... ...");

             Console.ReadLine();
         }

         static void CallBack(IAsyncResult result)
         {
             SendMessage sm = (SendMessage)((System.Runtime.Remoting.Messaging.AsyncResult)result).AsyncDelegate;
             Console.WriteLine(sm.EndInvoke(result));
         }

         static string DoAction(string msg)
         {
             Thread.Sleep();
             return msg;
         } 

         static  Task<string> DoTask(string msg)
         {
             return Task.Run(() =>
             {
                 Thread.Sleep();
                 return msg;
             });
         }

         static async void DoAsync(string msg)
         {
             Console.WriteLine(await DoTask(msg));
         }