Task取消

一：在Thread中做取消操作

声明一个变量取去判断Thread中是否可以退出。

bool res = false;
           var task = new Task(()=> {
               while (!res)
               {
                   Thread.Sleep(100);
                   Console.WriteLine("当前Thread={0}正在运行",Thread.CurrentThread.ManagedThreadId);
               }
           });
           task.Start();
           Thread.Sleep(1000);
           res = true;
           Console.Read();

不能让多个线程操作一个共享变量，否则会在release版本中有潜在bug

二：task中有专门的类CancellationTokenSource去处理“任务取消”

1.CancellationTokenSource远比一个变量强的多。

 CancellationTokenSource source = new CancellationTokenSource();
    var task = new Task(() => {
while (!source.IsCancellationRequested)
    {
        Thread.Sleep(100);
         Console.WriteLine("当前Thread={0}正在运行",Thread.CurrentThread.ManagedThreadId);
    }
 },source.Token);
task.Start();
Thread.Sleep(1000);
source.Cancel();

效果同上

2.当任务取消的时候，我希望有一个函数能够被触发，这个触发可以做一些资源的清理，又或者更新数据库信息

   CancellationTokenSource source = new CancellationTokenSource();
    source.Token.Register(()=> {
        //如果当前token被取消，此函数被执行
        Console.WriteLine("当前想线程被取消，可以做资源清理！");
    });
var task = new Task(() => {

    while (!source.IsCancellationRequested)
    {
        Thread.Sleep(100);
         Console.WriteLine("当前Thread={0}正在运行",Thread.CurrentThread.ManagedThreadId);
    }
},source.Token);
task.Start();
Thread.Sleep(1000);
source.Cancel();

3.延时取消：我想2秒之后自动取消，或者N秒

• source.CancelAfter(new TimeSpan(0,0,0,2));

• CancellationTokenSource 构造函数： CancellationTokenSource source = new CancellationTokenSource(1000);

• 取消组合，将CancellationTokenSource 组成一个链表，其中任何一个CancellationTokenSource 被取消，组合也会被取消。var s3=s1&s2;

CancellationTokenSource source1 = new CancellationTokenSource();
         source1.Cancel();
         CancellationTokenSource source2 = new CancellationTokenSource();

         var source3 = CancellationTokenSource.CreateLinkedTokenSource(source1.Token, source2.Token);


         Console.WriteLine("s1={0},s2={1},s3={2}",source1.IsCancellationRequested,source2.IsCancellationRequested,source3.IsCancellationRequested);

加了source1.Cancel();

不加source1.Cancel();

4.ThrowIfCancellationRequested

        CancellationTokenSource source1 = new CancellationTokenSource();
source1.Token.Register(()=> {
               Console.WriteLine("当前想线程被取消，可以做资源清理！");
           });
       var task = Task.Factory.StartNew(() =>
       {
           while (true)
           {
               source1.Token.ThrowIfCancellationRequested();
               Thread.Sleep(100);
               Console.WriteLine("当前Thread={0}正在运行", Thread.CurrentThread.ManagedThreadId);
           }
       }, source1.Token);
       Thread.Sleep(1000);
       source1.Cancel();

       Thread.Sleep(100);
       Console.WriteLine(task.Status);