示例一:

开发工具 Visual Studio 2012

.NET Framework 4.5

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

namespace AsyncTest
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Main-1");
            DoSomethingAsync();
            Console.WriteLine("Main-2");

            Console.Read();
        }

        static async Task DoSomethingAsync()
        {
            int val = 13;
            Console.WriteLine("val="+val);
            //异步方式等待1秒
            await Task.Delay(TimeSpan.FromSeconds(1));

            val *= 2;
            //异步方式等待1秒
            await Task.Delay(TimeSpan.FromSeconds(1));

            Console.WriteLine("val=" + val);
        }
    }
}

运行效果