C#—异步编程

C#异步编程基础

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

namespace AsyncBasic
{
    class OperateClass
    {
        #region 异步编程—创建任务
        /// <summary>
        /// 创建同步方法
        /// </summary>
        /// <param name="name"></param>
        /// <returns></returns>
        public static string Greeting(string name)
        {
            Thread.Sleep(3000);
            return string.Format("Hello,{0}",name);
        }

        /// <summary>
        /// 异步方法
        /// </summary>
        /// <param name="name"></param>
        /// <returns></returns>
        public static Task<string> GreetingAsync(string name)
        {
            return Task.Run<string>(()=>
            {
                return Greeting(name);
            });
        }
        #endregion

        #region 异步编程—调用异步方法
        /// <summary>
        /// 调用异步方法
        ///使用await关键字需要有用async修饰符声明的方法
        /// </summary>
        public async static void CallerWithAsync()
        {
            string result = await GreetingAsync("异步方法调用测试");
            Console.WriteLine(result); 
            //以上等价于
            Console.WriteLine(await GreetingAsync("输出方式二【异步方法调用测试】"));
        }
        #endregion

        #region 异步编程—延续任务
        /// <summary>
        /// 延续任务
        /// </summary>
        public static void CallerWithContinuationTask()
        {
            Task<string> t1 = GreetingAsync("延续任务");
            t1.ContinueWith(t =>
                {
                    string result = t.Result;
                    Console.WriteLine(result);
                });
        }
        #endregion

        #region 异步编程—使用多个异步方法
        /// <summary>
        /// 按顺序调用异步编程的方法
        /// </summary>
        public async static void MultipleAsyncMethods()
        {
            string s1 = await GreetingAsync("顺序1");
            string s2 = await GreetingAsync("顺序2");
            Console.WriteLine("两个方法的完成顺序");
            Console.WriteLine("Result 1:{0}\n Result 2:{1}",s1,s2);
        }

        /// <summary>
        /// 使用组合器
        /// 异步方法不依赖于其他其他异步方法，每个异步方法都不使用await
        /// 返回Task<string>
        /// </summary>
        public async static void MultipleAsyncMethodsWithCombinators1()
        {
            Task<string> t1 = GreetingAsync("组合器");
            Task<string> t2 = GreetingAsync("组合器1");
            await Task.WhenAll(t1,t2); //
            Console.WriteLine("两个方法的完成顺序:\n Result 1:{0}\n Result 2:{1}", t1.Result, t2.Result);
        }


        /// <summary>
        /// 使用组合器
        /// 异步方法不依赖于其他其他异步方法，每个异步方法都不使用await
        /// 返回数组
        /// </summary>
        public async static void MultipleAsyncMethodsWithCombinators1()
        {
            Task<string> t1 = GreetingAsync("组合器");
            Task<string> t2 = GreetingAsync("组合器1");
            string[] result = await Task.WhenAll(t1, t2); //
            Console.WriteLine("两个方法的完成顺序:\n Result 1:{0}\n Result 2:{1}", result[0], result[1]);
        }

        #endregion

        #region 异步编程—转换异步模式
        //在没有提供基于任务的异步编程模式下，使用BegainXXX和EndXXX转换异步模式

        /// <summary>
        /// 声明同步的一个委托
        /// </summary>
        private static Func<string, string> greetingInvoker = Greeting;

        //接受三个参数，返回IAsyncResult
        public static IAsyncResult BeginGreeting(string name, AsyncCallback callback, object state)
        {
            return greetingInvoker.BeginInvoke(name,callback,state);
        }
        
        //
        public static string EndGreeting(IAsyncResult ar)
        {
            return greetingInvoker.EndInvoke(ar);
        }

        //
        public static async void ConvertingAsyncPattern()
        {
            string s = await Task<string>.Factory.FromAsync<string>(BeginGreeting, EndGreeting, "转换模式", null);
            Console.WriteLine(s);
        }
        #endregion

        #region 异步编程—错误处理
        /// <summary>
        /// 延迟后抛出一个异常
        /// </summary>
        /// <param name="ms"></param>
        /// <param name="message"></param>
        /// <returns></returns>
        public static async Task ThrowAfter(int ms, string message)
        {
            await Task.Delay(ms);
            throw new Exception(message);
        }

        /// <summary>
        /// 异步方法的异常处理（2s后抛出异常）
        /// </summary>
        public static async void HandleOneError()
        {
            try
            {
                await ThrowAfter(2000, "first");
            }
            catch(Exception ex)
            {
                Console.WriteLine("handled {0}", ex.Message);
            }
        }

        /// <summary>
        /// 多个异步方法的异常处理
        /// 第二个异常不被抛出，抛出第一个异常开始处理
        /// </summary>
        public static async void StartTwoTasks()
        {
            try
            {
                await ThrowAfter(2000, "first");
                await ThrowAfter(1000, "second");

            }
            catch (Exception ex)
            {
                Console.WriteLine("handled {0}", ex.Message);
            }
        }

        /// <summary>
        /// 多个异步方法的异常处理
        /// 获取多个异常后再处理(只能看见第一个任务的异常)
        /// </summary>
        public static async void StartTwoTasksParallel()
        {
            try
            {
                Task t1 = ThrowAfter(2000, "first");
                Task t2 = ThrowAfter(1000, "second");
                await Task.WhenAll(t1, t2);
            }
            catch (Exception ex)
            {
                Console.WriteLine("handled {0}",ex.Message);
            }
        }

        /// <summary>
        /// 多个异步方法的异常处理
        /// 获取多个异常后再处理(遍历所有异常)
        /// </summary>
        public static async void ShowAggregateException()
        {
            Task taskResult = null;
            try
            {
                Task t1 = ThrowAfter(2000, "first");
                Task t2 = ThrowAfter(1000, "second");
                await (taskResult = Task.WhenAll(t1, t2));
            }
            catch (Exception ex)
            {
                Console.WriteLine("handled {0}",ex.Message);
                foreach (var ex1 in taskResult.Exception.InnerExceptions)
                {
                    Console.WriteLine("inner exception {0}",ex1.Message);
                }
            }
        }
        #endregion

        #region 异步编程—取消任务
        //.NET 4.0开始提供了一种标准的机制，基于任务的异步模式
        /// <summary>
        /// 取消任务
        /// </summary>
        public partial class MainWindow : Window
        {
            private object lockList = new object();
            private CancellationTokenSource cts;

            /// <summary>
            /// 开始取消任务
            /// </summary>
            /// <param name="sender"></param>
            /// <param name="e"></param>
            private void onCancel(object sender, RoutedEventArgs e)
            {
                if (cts != null)
                {
                    cts.Cancel();
                }
            }

            //2.使用框架取消任务
            //框架中的某些异步方法通过提供可以传入的CancellationToken的重载来支持取消任务
            //3.取消自定义的任务
            private async void CanelCustomTask()
            {
                await Task.Run(() =>
                    {
                        cts.Token.ThrowIfCancellationRequested();
                    },cts.Token);
            }
          
         
        }

       

        #endregion
    }
}