如何捕捉CancellationToken.ThrowIfCancellationRequested

Question

这段代码执行时

cancellationToken.ThrowIfCancellationRequested();

try catch 块不处理 exception。

    public EnumerableObservable(IEnumerable<T> enumerable)
    {
        this.enumerable = enumerable;
        this.cancellationSource = new CancellationTokenSource();
        this.cancellationToken = cancellationSource.Token;


        this.workerTask = Task.Factory.StartNew(() =>
        {
            try
            {
                foreach (var value in this.enumerable)
                {
                    //if task cancellation triggers, raise the proper exception
                    //to stop task execution

                    cancellationToken.ThrowIfCancellationRequested();

                    foreach (var observer in observerList)
                    {
                        observer.OnNext(value);
                    }
                }
            }
            catch (AggregateException e)
            {
                Console.Write(e.ToString());                    
            }
        }, this.cancellationToken);

    }

Answer 1

由于 ThrowIfCancellationRequested() 抛出类型为 OperationCanceledException 的异常，您必须捕获 OperationCanceledException 或其基础之一 类。

https://msdn.microsoft.com/en-us/library/system.operationcanceledexception(v=vs.110).aspx

Answer 2

AggregateExceptions are thrown when a possible multitude of exceptions during asynchronous operations occured. They contain all exceptions that were raised e.g. in chained Tasks (via .ContinueWith) or within cascaded async/await 调用。

正如@Mitch Stewart 指出的那样，在您的示例中，要处理的正确异常类型是 OperationCancelledException。