c#-4.0 - 错误 : The operation was canceled

Question

我正在使用此代码片段执行带有取消标记的异步查询:

var _client = new HttpClient( /* some setthngs */ );

_client.GetAsync(someUrl, cancellationToken).ContinueWith(gettingTask => {
    cancellationToken.ThrowIfCancellationRequested();
    SomeStuffToDO();
    }, TaskScheduler.FromCurrentSynchronizationContext());
}, TaskScheduler.FromCurrentSynchronizationContext());

但是，当操作被取消时，cancellationToken.ThrowIfCancellationRequested(); 会抛出异常。我知道这条线应该到这个东西。但是，在开发环境中，异常会导致 visual studio 中断。我怎样才能避免这种情况？

Answer 1

你需要在 lambda 中处理，像这样:

var _client = new HttpClient( /* some setthngs */ );

_client.GetAsync(someUrl, cancellationToken).ContinueWith(gettingTask => {
    try {
     cancellationToken.ThrowIfCancellationRequested();
     SomeStuffToDO();
    }
    catch (...) { ... }
    finaly { ... }
    }, TaskScheduler.FromCurrentSynchronizationContext());
}, TaskScheduler.FromCurrentSynchronizationContext());

但 _client.GetAsync(someUrl, cancellationToken) 也可能抛出取消​​异常，因此您需要使用 try-catch 包装该调用(或等待其包含方法的位置)。