如何在c#控制台应用程序中自动（强制）停止当前线程[重复]

Question

大家好，我是多线程编码的新手，我的任务是更改当前工作控制台应用程序的流程。当前，当控制台应用程序启动时，它会通过以下代码。 “Task.Factory.Startnew”方法启动新线程并运行“CheckDatabaseFieldStatus”，它正在检查数据库表字段的状态。如果该字段有“取消”值，那么它将调用 Token.cancel() 方法。

同时，当前线程正在执行某种逻辑，不断调用“CheckCancelTokenStatus”函数抛出“ThrowIfCancellationRequested”异常。

新要求：我想从另一个由“Task.Factory.Startnew”方法创建的线程中停止当前线程。如何以安全的方式从另一个线程强制取消当前线程？

代码如下：

public CancellationTokenSource TokenSource = new CancellationTokenSource();
public CancellationToken Token = TokenSource.Token;
try
{

// Spin up a task that will keep checking the request to see if it has been cancelled.
Task cancelCheck = Task.Factory.StartNew(CheckDatabaseFieldStatus, TaskCreationOptions.LongRunning);

//Some logic to finish task

CheckCancelTokenStatus(Token);

//Some logic to finish task

CheckCancelTokenStatus(Token);

//Some logic to finish task

CheckCancelTokenStatus(Token);

//Some logic to finish task

}
catch (OperationCanceledException){
    
   
   //Database call to Update status of task to canceled

}

//here is dispose method dispose token

这里是函数“CheckDatabaseFieldStatus”

public void CheckDatabaseFieldStatus()
        {
            // While a Request is running, we're going to keep polling to check if we want to cancel.
            while (!Token.IsCancellationRequested)
            {
                // Using the request timer here for our wait would mean that requests could take up to 30 
               seconds to finish after they've actually finished.
                Thread.Sleep(5000);

                // Create a new context with each check to avoid conflicts with main context
                using (DbContext mydb= new DbContext())
                {
                    

                    // Get the newest version of the request and check if it's set to cancel.
                    if (mydb.Table.GetAll().Any(r => r.Status=="cancelling"))
                       {
                        TokenSource.Cancel();
                       }
                }
            }
      }

这里是 CheckCancelTokenStatus 函数

function CheckCancelTokenStatus(CancellationToken Token)
{
     if (Token.HasValue && Token.Value.IsCancellationRequested)
         {
               Token.Value.ThrowIfCancellationRequested();
          }
}

Answer 1

尝试使用Task.Delay(int milliseconds, CancellationToken token)，而不是使用Thread.Sleep。 Task.Delay 创建将在给定延迟后完成的任务。如果令牌在等待期间被取消，它将抛出异常并停止执行。在等待取消之前和之后最好检查一下，因为有人可能会在你睡觉时取消执行。

public void CheckDatabaseFieldStatus()
        {
            while (!Token.IsCancellationRequested)
            {
                Task.Delay(5000, Token).GetAwaiter().GetResult();
                Token.ThrowIfCancellationRequested();

                using (DbContext mydb= new DbContext())
                {
                    if (mydb.Table.GetAll().Any(r => r.Status=="cancelling"))
                    {
                        TokenSource.Cancel();
                    }
                }
            }
      }

我也使用GetAwaiter().GetResult() 而不是简单的Wait()，因为第二个选项包含异常。请参阅此答案以获取解释https://stackoverflow.com/a/38530225/10339675

一般来说最好使用async/await而不是同步等待