【C#】async与await介绍

1. 实例1

1.1 代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace ConsoleApp1
{class Program{static void Main(string[] args){Method1();Method2();Console.ReadKey();}public static async Task Method1(){Console.WriteLine("Method 1 Start................");await Task.Run(() =>{for (int i = 0; i < 100; i++){Console.WriteLine(" Method 1");}});//await的Task运行完以后，下面的代码才运行Console.WriteLine("Method 1 End................");}public static void Method2(){for (int i = 0; i < 25; i++){Console.WriteLine(" Method 2");}}}
}

1.2 运行结果

Method2不会等待Method1运行结束再运行。
async方法中，await后面的代码也要等待await运行结束以后再运行。

2. 实例2

2.1 代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace ConsoleApp2
{class Program{static void Main(string[] args){callMethod();Console.ReadKey();}public static async void callMethod(){//方式1，Method3需要等待Method1的结果，所以Method1与Method2交替执行，Method3等Method1执行完毕再执行//await之后的需要等待前面的运行完再运行。Task<int> task = Method1();Method2();int count = await task;Method3(count);//方式2，顺序执行，运行完Method1再运行Method2再运行Method3//int count = await Method1();//Method2();//Method3(count);//方式3，报错。必须加await//int count = Method1();//Method2();//Method3(count);//方式4,Method1与[Method2,Method3]交替运行，Method2和Method3顺序执行//Method1();//Method2();//Method3(4);}public static async Task<int> Method1(){int count = 0;await Task.Run(() =>{for (int i = 0; i < 100; i++){Console.WriteLine(" Method 1");count += 1;}});return count;}public static void Method2(){for (int i = 0; i < 25; i++){Console.WriteLine(" Method 2");}}public static void Method3(int count){Console.WriteLine(" Method 3 Total count is " + count);}}
}