• Async和Await


      1     public class AwaitAsyncShow
      2     {
      3         public static void Show()
      4         {
      5             Test();
      6         }
      7         private async static Task Test()
      8         {
      9             Console.WriteLine($"当前主线程id={Thread.CurrentThread.ManagedThreadId}");
     10             {
     11                 //NoReturnNoAwait();
     12             }
     13             {
     14                 //NoReturn();
     15                 //for (int i = 0; i < 10; i++)
     16                 //{
     17                 //    Thread.Sleep(300);
     18                 //    Console.WriteLine($"Main Thread Task ManagedThreadId={Thread.CurrentThread.ManagedThreadId} i={i}");
     19                 //}
     20             }
     21             {
     22                 //Task t = NoReturnTask();
     23                 //Console.WriteLine($"Main Thread Task ManagedThreadId={Thread.CurrentThread.ManagedThreadId}");
     24                 //t.Wait();//主线程等待Task的完成
     25                 //await t;//await后的代码会由  子线程执行
     26             }
     27             {
     28                 Task<long> t = SumAsync();
     29                 Console.WriteLine($"Main Thread Task ManagedThreadId={Thread.CurrentThread.ManagedThreadId}");
     30                 long lResult = t.Result;//访问result 主线程等待Task的完成
     31                 t.Wait();//等价于上一行
     32             }
     33 
     34             Console.Read();
     35         }
     36 
     37         /// <summary>
     38         /// 只有async没有await,会有个warn
     39         /// 跟普通方法没有区别
     40         /// </summary>
     41         private static async void NoReturnNoAwait()
     42         {
     43             //主线程执行
     44             Console.WriteLine($"NoReturnNoAwait Sleep before Task,ThreadId={Thread.CurrentThread.ManagedThreadId}");
     45             Task task = Task.Run(() =>
     46             {
     47                 Console.WriteLine($"NoReturnNoAwait Sleep before,ThreadId={Thread.CurrentThread.ManagedThreadId}");
     48                 Thread.Sleep(3000);
     49                 Console.WriteLine($"NoReturnNoAwait Sleep after,ThreadId={Thread.CurrentThread.ManagedThreadId}");
     50             });
     51 
     52             //主线程执行
     53             Console.WriteLine($"NoReturnNoAwait Sleep after Task,ThreadId={Thread.CurrentThread.ManagedThreadId}");
     54         }
     55 
     56         /// <summary>
     57         /// async/await
     58         /// 不能单独await
     59         /// await只能放在task前面
     60         /// 不推荐void返回值,使用Task来代替
     61         /// Task和Task<T>能够使用await,Task.WhenAny,Task.WhenAll等方式组合使用。Async Void 不行
     62         /// </summary>
     63         private static async void NoReturn()
     64         {
     65             //主线程执行
     66             Console.WriteLine($"NoReturn Sleep before await,ThreadId={Thread.CurrentThread.ManagedThreadId}");
     67             TaskFactory taskFactory = new TaskFactory();
     68             Task task = taskFactory.StartNew(() =>
     69             {
     70                 Console.WriteLine($"NoReturn Sleep before,ThreadId={Thread.CurrentThread.ManagedThreadId}");
     71                 Thread.Sleep(3000);
     72                 Console.WriteLine($"NoReturn Sleep after,ThreadId={Thread.CurrentThread.ManagedThreadId}");
     73             });
     74             await task;//主线程在这里就返回来,执行主线程任务去了
     75 
     76             //耗时任务就用await
     77 
     78             //子线程执行 其实是封装成委托,在task之后成为回调(编译器功能,状态机实现)
     79             //task.ContinueWith()
     80             //这个回调的线程是不确定的:可能是主线程,可能是子线程,也可能是其他线程
     81             Console.WriteLine($"NoReturn Sleep after Task,ThreadId={Thread.CurrentThread.ManagedThreadId}");
     82         }
     83 
     84         /// <summary>
     85         /// 无返回值 async Task==async void
     86         /// Task和Task<T>能够使用await,Task.WhenAny,Task.WhenAll等方式组合使用。Async void不行
     87         /// </summary>
     88         /// <returns></returns>
     89         private static async Task NoReturnTask()
     90         {
     91             //这里是主线程的Id
     92             Console.WriteLine($"NoReturnTask Sleep before await,ThreadId={Thread.CurrentThread.ManagedThreadId}");
     93             await Task.Run(() =>
     94             {
     95                 Console.WriteLine($"NoReturnTask Sleep before,ThreadId={Thread.CurrentThread.ManagedThreadId}");
     96                 Thread.Sleep(3000);
     97                 Console.WriteLine($"NoReturnTask Sleep after,ThreadId={Thread.CurrentThread.ManagedThreadId}");
     98             });
     99             //await task
    100             Console.WriteLine($"NoReturnTask Sleep after await,ThreadId={Thread.CurrentThread.ManagedThreadId}");
    101 
    102             //return new TaskFactory().StartNew(() => { });//不能return 没有async才行
    103         }
    104 
    105         /// <summary>
    106         /// 待返回至的Task 要使用返回值就一定要等到子线程计算完毕
    107         /// </summary>
    108         /// <returns></returns>
    109         private static async Task<long> SumAsync()
    110         {
    111             Console.WriteLine($"SumAsync 111 start ManagedThreadId={Thread.CurrentThread.ManagedThreadId}");
    112             long result = 0;
    113 
    114             await Task.Run(() =>
    115             {
    116                 for (int i = 0; i < 10; i++)
    117                 {
    118                     Console.WriteLine(
    119                         $"SumAsync {i} await Task.Run ManagedThreadId={Thread.CurrentThread.ManagedThreadId}");
    120                     Thread.Sleep(1000);
    121                 }
    122 
    123                 for (long k = 0; k < 999999999; k++)
    124                 {
    125                     result += k;
    126                 }
    127             });
    128             Console.WriteLine($"SumFactory 111 end ManagedThreadId={Thread.CurrentThread.ManagedThreadId}");
    129             return result;
    130         }
    131 
    132         /// <summary>
    133         /// 真的返回Task 不是async 要使用返回值就一定要等子线程计算完毕
    134         /// </summary>
    135         /// <returns></returns>
    136         private static Task<int> SumFactory()
    137         {
    138             Console.WriteLine($"SumFactory 111 start ManagedThreadId={Thread.CurrentThread.ManagedThreadId}");
    139             TaskFactory taskFactory=new TaskFactory();
    140             Task<int> iResult= taskFactory.StartNew<int>(() =>
    141             {
    142                 Thread.Sleep(3000);
    143                 Console.WriteLine(
    144                     $"SumFactory 123 Task.Run ManagedThreadId={Thread.CurrentThread.ManagedThreadId}");
    145                 
    146                 return 123;
    147             });
    148             Console.WriteLine($"SumFactory 111 end ManagedThreadId={Thread.CurrentThread.ManagedThreadId}");
    149             return iResult;
    150         }
    151     }
    View Code
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  • 原文地址:https://www.cnblogs.com/shangec/p/10311524.html
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