c# 异步编程demo (async await)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Web;
using System.Threading;
using System.Threading.Tasks;

namespace TestApp
{
    class Program
    {
        static void Main(string[] args)
        {
            Task<string> task = Call();
            Console.WriteLine("测试");
            Console.WriteLine(task.Result);
            
        }
        static string Greeting(string name)
        {
            Thread.Sleep(3000);
            return string.Format("Hello, {0}", name);

        }
        static Task<string> GreetingAsync(string name)
        {
            return Task.Run<string>(() => { return Greeting(name); });
        }
        private async static Task<string> Call()
        {

            string result = await GreetingAsync("world");
            return result;
        }

    }
}