我使用下面的代码在
WPF页面异步方式中执行耗时的操作以及向UI报告进度
private void btnStart_Click(object sender,RoutedEventArgs e) { txt_importStatus.Text = ""; var progress = new Progress<string>(progress_info => { //show import progress on a textfield txt_importStatus.Text = progress_info + Environment.NewLine + "Please dont close this window while the system processing the excel file contents"; }); // DoProcessing is run on the thread pool. await Task.Run(() => DoProcessing(progress)); } public void DoProcessing(IProgress<string> progress) { //read an excel file and foreach excel file row foreach(excelrow row in excelrowlist) { //do db entry and update UI the progress like progress.Report("Processed x number of records. please wait.."); } }
现在我想添加一个额外的选项,在中间取消这个异步操作.为此我发现我必须添加以下选项
CancellationTokenSource tokenSource = new CancellationTokenSource(); CancellationToken token = tokenSource.Token; private void btnCacnel_Click(object sender,RoutedEventArgs e) { tokenSource.Cancel(); }
但是如何将此tokenSource传递给我的DoProcessing调用以及如何在DoProcessing中处理取消
解决方法
实际上,您不需要将CancellationTokenSource传递给DoProcessing,而只需要将CancellationToken传递给DoProcessing.
为了处理取消,您可以执行以下操作:
public void DoProcessing(CancellationToken token,IProgress<string> progress) { //read an excel file and foreach excel file row foreach(excelrow row in excelrowlist) { if(token.IsCancellationRequested) break; //do db entry and update UI the progress like progress.Report("Processed x number of records. please wait.."); } }
在这种情况下,您需要在btnStart_Click中创建取消令牌源.如果不清楚,你需要这样做:
CancellationTokenSource tokenSource; private void btnStart_Click(object sender,RoutedEventArgs e) { txt_importStatus.Text = ""; var progress = new Progress<string>(progress_info => { //show import progress on a textfield txt_importStatus.Text = progress_info + Environment.NewLine + "Please dont close this window while the system processing the excel file contents"; }); // DoProcessing is run on the thread pool. tokenSource = new CancellationTokenSource(); var token = tokenSource.Token; await Task.Run(() => DoProcessing(token,progress)); }
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