How to Properly Cancel an `await`-ing WinRT Task?

Effectively cancels the task if await is used

When working with a WinRT task, you may try to terminate the task using the CancelNotification method. However, this code may cause unexpected results because the task will actually continue to complete even if you try to cancel. In order to overcome this limitation and actually stop the task when cancelled, follow these steps:

Integrate cancellation functionality into your method by passing the CancellationToken object. Ensure that every method that can be terminated periodically validates this token.

The modified code snippet effectively cancels the task as expected:

<code class="language-csharp">private async Task TryTask()
{
  CancellationTokenSource source = new CancellationTokenSource();
  source.CancelAfter(TimeSpan.FromSeconds(1));
  Task<int> task = Task.Run(() => slowFunc(1, 2, source.Token), source.Token);

  try
  {
    await task;
  }
  catch (OperationCanceledException)
  {
    // 处理取消
  }
}

private int slowFunc(int a, int b, CancellationToken cancellationToken)
{
  string someString = string.Empty;
  for (int i = 0; i < 1000000; i++)
  {
    someString += i.ToString();
    cancellationToken.ThrowIfCancellationRequested(); // 定期检查取消请求
  }
  return a + b;
}</code>

By using the await block within the try/catch action, you can handle the OperationCanceledException and take appropriate actions to mitigate the effects of task cancellation.

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