c# - 使用 async 代替 Task.Run()

Question

我有以下代码:

private void btnAction_Click(object sender, RoutedEventArgs e)
{

    /** Clear the results field */
    txtResult.Text = "";

    /** Disable the button and show waiting status */
    btnAction.IsEnabled = false;
    lblStatus.Text = "Wait...";

    /** Get input from the query field */
    string input = query.Text;

    /** Run a new task */
    Task.Run(() => {

        // calling a method that takes a long time (>3s) to finish and return
        var attempt = someLibrary.doSomethingWith(input);

        // return the result to the GUI thred
        this.Dispatcher.Invoke(() =>
        {

            if (attempt.ContainsKey("success"))
            {
                if (attempt["success"] == true)
                {
                    txtResult.Text = "Success! The door is: " + (attempt["is_open"] ? "open" : "closed");
                    lblStatus.Text = "";
                }
                else
                {
                    lblStatus.Text = "Error! The service says: " + attempt["errorMessage"];
                }
            }

            else
            {
                MessageBox.Show("There was a problem getting results from web service.");
                lblStatus.Text = "";
            }

            /** Re-enable the button */
            btnAction.IsEnabled = true;

        });
    });

}

现在，我想:

• 以使用回调的方式编写相同的代码，而不是使用 Dispatcher.Invoke()。
• 能够取消调用 doSomething() 的正在运行的任务
• 能够链接多个调用，即等待 doSomething() 并在完成后使用上一次调用的结果 doAnotherThing()

这就是为什么我想使用异步模型来编写它。

我该怎么办？

Answer 1

您可以将您的方法标记为async，await Task.Run，以便延续在UI，也只保留长时间运行(看似受 CPU 限制)作业

private async void btnAction_Click(object sender, RoutedEventArgs e)
{
   btnAction.IsEnabled = false;
   txtResult.Text = "";       
   lblStatus.Text = "Wait...";

   string input = query.Text;

   // calling a method that takes a long time (>3s) to finish and return
   var attempt =  await Task.Run(() => someLibrary.doSomethingWith(input));

   if (attempt.ContainsKey("success"))
   {
      if (attempt["success"] == true)
      {
         txtResult.Text = "Success! The door is: " + (attempt["is_open"] ? "open" : "closed");
         lblStatus.Text = "";
      }
      else
      {
         lblStatus.Text = "Error! The service says: " + attempt["errorMessage"];
      }
   }  
   else
   {
      MessageBox.Show("There was a problem getting results from web service.");
      lblStatus.Text = "";
   }

   btnAction.IsEnabled = true;

}

更新

要取消任务，您可以使用 CancellationTokenSource 实例中的 CancellationToken 并将其传递到 Task.Run 以及您的 long运行方法来检查 IsCancellationRequested (如果可以的话)。您可以通过调用 CancellationTokenSource.Cancel

取消

请注意，您可能希望将其包装在 try catch finally 中，并捕获 OperationCanceledException 并将按钮启用代码放在 finally