如何停止导致 IAsyncOperation 的调用？

Question

在我的应用程序中，我通知了多个设备。如果某个设备在几秒钟内无法接通并且没有响应，我想取消通话。

我的代码是：
await characteristic0.WriteClientCharacteristicConfigurationDescriptorAsync (GattClientCharacteristicConfigurationDescriptorValue.Notify);

现在经过一些研究，我发现通常可以传递 CancelationToken (_ct) 并执行此操作：

首先创建一个包含调用的操作：
IAsyncOperation<GattCommunicationStatus> operation = characteristic0.WriteClientCharacteristicConfigurationDescriptorAsync (GattClientCharacteristicConfigurationDescriptorValue.Notify);

然后使用 CancellationToken 创建任务：
Task<GattCommunicationStatus> task = operation.AsTask(_ct);

然后等待它：
GattCommunicationStatus status = await task;

现在，即使 CancellationToken 的 IsCancellationRequested-属性设置为 true，情况也是如此。通话不会停止。
而且，设备已经在第一行之后收到 Notified！这不是应该在调用 await 之后发生吗？？

是我用错了令牌还是这是一个更大的东西？

编辑
在与@Andrii Litvinov 交谈后，我在最初的问题描述中添加了一些代码。这是整个方法：

public async Task<GattCommunicationStatus> NotifyDevice(DeviceInformationDisplay deviceInfo, CancellationToken _ct)
        {
            try
            {
                BluetoothLEDevice device = await BluetoothLEDevice.FromIdAsync(deviceInfo.Id);
                service = device.GetGattService(new Guid(Service_UUID));
                characteristic0 = service.GetCharacteristics(new Guid(Characteristic_0_UUID)).First();

                characteristic0.ValueChanged += characteristic0ValueChanged;
                GattCommunicationStatus status = await characteristic0.WriteClientCharacteristicConfigurationDescriptorAsync(GattClientCharacteristicConfigurationDescriptorValue.Notify);
                _ct.Register(() =>
                {
                // trying to cancel the operation somehow
                });
                IAsyncOperation<GattCommunicationStatus> operation = characteristic0.WriteClientCharacteristicConfigurationDescriptorAsync(GattClientCharacteristicConfigurationDescriptorValue.Notify);
                Task<GattCommunicationStatus> task = operation.AsTask(_ct);
                GattCommunicationStatus status_1 = await task;

                if (!elapsedTimeWatcher.IsRunning)
                {
                    elapsedTimeWatcher.Start();
                }

                else
                {
                    elapsedTimeWatcher.Restart();
                }
                return status;
            }
            catch(OperationCanceledException e)
            {
                return GattCommunicationStatus.Unreachable;
            }
            catch (Exception e)
            {
                return GattCommunicationStatus.Unreachable;
            }

        }

Answer 1

基于 docs 你做得对：

try
{
...

IAsyncOperation<GattCommunicationStatus> operation =
    characteristic0.WriteClientCharacteristicConfigurationDescriptorAsync(
        GattClientCharacteristicConfigurationDescriptorValue.Notify);
return await operation.AsTask(_ct);

...
}
...

此代码应注册到令牌并在后台调用 operation.Cancel()。

能否将令牌设置为较低的值以查看操作是否真的被取消？执行该方法通常需要多少时间？

尝试：

CancellationTokenSource cts = new CancellationTokenSource(10);
await NotifyDevice(BLEDevice, cts.Token);

甚至更低的值。

如何停止导致 IAsyncOperation 的调用？

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