C# 带有令牌的TaskCompletionSource
我使用Scandit框架创建了扫描方法。因为我使用的是Xamarin.Forms,所以没有等待扫描的选项。Scandit准备了作为扫描结果的回调。我想把它包装成一个方法,可以与waiter一起使用 以下是我所做的:C# 带有令牌的TaskCompletionSource,c#,multithreading,C#,Multithreading,我使用Scandit框架创建了扫描方法。因为我使用的是Xamarin.Forms,所以没有等待扫描的选项。Scandit准备了作为扫描结果的回调。我想把它包装成一个方法,可以与waiter一起使用 以下是我所做的: public async Task<Operation<string>> ScanAsync(CancellationToken cancellationToken = default(CancellationToken)) {
public async Task<Operation<string>> ScanAsync(CancellationToken cancellationToken = default(CancellationToken))
{
try
{
_codeScannedTcs = new TaskCompletionSource<Operation<string>>();
ScanditService.BarcodePicker.DidScan += OnScanFinished;
await ScanditService.BarcodePicker.StartScanningAsync();
var result = await Task.WhenAny(_codeScannedTcs.Task);
return result.Result;
}
catch (TaskCanceledException)
{
return Operation<string>.FailedOperation("A task was canceled");
}
catch (Exception ex)
{
return Operation<string>.FailedOperation(ex.Message);
}
finally
{
_codeScannedTcs = null;
ScanditService.BarcodePicker.DidScan -= OnScanFinished;
}
}
public async Task scanaync(CancellationToken CancellationToken=default(CancellationToken))
{
尝试
{
_codeScannedTcs=新任务完成源();
ScanditService.BarcodePicker.DidScan+=OnScanFinished;
等待ScanditService.BarcodePicker.StartScanningAsync();
var result=wait Task.wheny(_codeScannedTcs.Task);
返回结果。结果;
}
捕获(TaskCanceledException)
{
返回操作。失败操作(“任务被取消”);
}
捕获(例外情况除外)
{
返回操作。失败操作(例如消息);
}
最后
{
_codeScannedTcs=null;
ScanditService.BarcodePicker.DidScan-=OnScanFinished;
}
}
在这种情况下,我如何使用取消令牌随时中断扫描?我过去使用过以下代码:
/// <summary>
/// Allows the code waiting for an async operation to stop waiting when the cancellation token is set.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="task"></param>
/// <param name="cancellationToken"></param>
/// <see cref="https://blogs.msdn.microsoft.com/pfxteam/2012/10/05/how-do-i-cancel-non-cancelable-async-operations/"/>
/// <returns></returns>
public static async Task<T> WithCancellation<T>(this Task<T> task, CancellationToken cancellationToken)
{
var tcs = new TaskCompletionSource<bool>();
using (cancellationToken.Register(x => ((TaskCompletionSource<bool>)x).TrySetResult(true), tcs))
{
if (task != await Task.WhenAny(task, tcs.Task))
throw new OperationCanceledException(cancellationToken);
}
return await task;
}
//
///设置取消令牌时,允许等待异步操作的代码停止等待。
///
///
///
///
///
///
取消的公共静态异步任务(此任务任务,取消令牌取消令牌)
{
var tcs=new TaskCompletionSource();
使用(cancellationToken.Register(x=>((TaskCompletionSource)x.TrySetResult(true),tcs))
{
if(task!=等待task.wheny(task,tcs.task))
抛出新操作CanceledException(cancellationToken);
}
返回等待任务;
}
它可以是从它粘贴的逐字复制品,也可以是它的派生品