如何在c#metro应用程序中停止异步任务

Question

我正在使用c#开发metro应用程序,我正在使用async并等待关键字来创建make metro异步操作(下载数据等).我总是显示模态"请等待"对话框.我想在此模态对话框中添加"取消"按钮以允许取消后台操作.但我不知道如何取消处理任务...有没有任何示例如何做到这一点？

这是我的任务的例子:

// Starts task
public void StartTask()
{
    // show the modal dialog with progress
    _progressDialog.IsOpen = true;
    _progressDialog.CancelClick += ProgressDialog_CancelClick;
    await ToWork();
    _progressDialog.IsOpen = false;
}


// Task which takes some seconds
private async Task DoWork()
{
   await DownloadData();
   await ProcessData();
}

// Cancel task
private void CancelClick(object sender, RoutedEventArgs e)
{
    // hide the modal dialog with progress        
    _progressDialog.IsOpen = false;
    // TODO: Cancel task
    GoBack(this, e);
}

Answer 1

你可以决定实现DownloadData并ProcessData使得它们采取CancellationToken并传递给他们,当您需要取消.

public Task DownloadData(CancellationToken tok)
{
    tok.ThrowIfCancellationRequested();//check that it hasn't been cancelled.

   //while doing your task check

  if (tok.IsCancellationRequested)
    {
                    // whatever you need to clean up.
                    tok.ThrowIfCancellationRequested();
     }


}

对于用法,您可以创建一个CancellationTokenSource并将令牌传递给该方法.

var source = new CancellationTokenSource();

await DownloadData(source.Token);

当您需要取消时,您可以呼叫Cancel()来源

source.Cancel();