async & await 异步编程小示例，一看就懂

 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
 
 namespace ConAppAsync
 {
     class Program
     {
 
         //第一步，创建一个普通的耗时的方法
         static string Greeting(string name)
         {
             Thread.Sleep();
             return String.Format("Hello, {0}", name);
         }
 
         //第二步，用一个异步方法包装上面的方法
         static Task<string> GreetingAsync(string name)
         {
             return Task.Run<string>(() =>
             {
                 return Greeting(name);
             });
         }
 
         //第三步，再创建一个能调用上面的异步方法的方法, 加关键字 async
 
         private async static void CallWithAsync()
         {
             //some other tasks
 
             string result = await GreetingAsync("王海滨");
 
             //we can add multiple "await" in same "async" method
             string result1 = await GreetingAsync("Ahmed");
             string result2 = await GreetingAsync("Every Body");
             Console.WriteLine(result+result1+result2);
         }
 
         static void Main(string[] args)
         {
             //最后在主入口调用上面的方法，和调用普通方法一样
             CallWithAsync();
             int length = ;
             for (int i = ; i < length; i++)
             {
                 Console.WriteLine(i);
             }
             Console.ReadKey();
         }
     }
 }