C＃如何通过单击另一个按钮来取消task.run？ [英] C# how to cancel task.run by click on another button?

问题描述

hi
i希望通过点击另一个按钮取消当前任务

如何？



我有什么试过：

hi i want cancel current task run by click on another button
how?

What I have tried:

private async void Search_Button_ClickAsync(object sender, EventArgs e)
        {
             await (Task.Run(() =>
			 //... my program
			 ));
        }

private async void CancelButton_ClickAsync(object sender, EventArgs e)
        {
// i want cancel by click this button
        }		

推荐答案

您可以使用 CancellationTokenSource 执行此操作，请参阅此处的示例：并行编程：任务取消| C＃常见问题解答 [ ^ ]

您将需要以下语法：

You can do this with a CancellationTokenSource see example here: Parallel Programming: Task Cancellation | C# Frequently Asked Questions[^]
You will need this syntax though:

Task.Factory.StartNew()

您需要在方法中检查是否已请求取消。以下是来自ViewModel的片段，用于显示您需要的模式。

You need to check within your method to see if cancellation has been requested. Here is a snippet from a ViewModel to show the sort of pattern you need.

 private CancellationTokenSource cts;
//called from a 'start' button click
 private async void OnStartAsync(object arg)
        {
            IsStarted = true;

            cts = new CancellationTokenSource();
            CancellationToken token = cts.Token;
            try
            {
                //this runs your asynchronous method
                //you must check periodically to see 
                //if cancellation has been requested
                await Task.Run(() =>
                {
                    while (true)
                    {
                        Thread.Sleep(100);
                        //check to see if operation is cancelled
                        //and throw exception if it is
                        token.ThrowIfCancellationRequested();
                    }
                },token);
            }
            catch (OperationCanceledException)
            {
                IsStarted = false;

            }


        }

        private bool isStarted;
        public bool IsStarted
        {
            get
            {
                return isStarted;
            }
            set
            {
                isStarted = value;
                StartCommand.RaiseCanExecuteChanged();
                CancelCommand.RaiseCanExecuteChanged();

            }
        }

         //called from a 'cancel' button
        private void OnCancel(object arg)
        {
            cts.Cancel();
          
        }

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