如何在使用ContinueWith时捕获OperationCanceledException

我有一些代码，我正在从。net 4.5的可爱的async和await关键字降级到。net 4.0。我使用ContinueWith来创建一个类似于await工作方式的延续。

基本上，我的旧代码是:

var tokenSource = newCancellationTokenSource();
var myTask = Task.Run(() =>
{
    return MyStaticClass.DoStuff(tokenSource.Token);
}, tokenSource.Token);
try
{
    var result = await myTask;
    DoStuffWith(result);
}
catch (OperationCanceledException)
{
    // Cancel gracefully.
}

(如人们所料，MyStaticClass.DoStuff(token)经常调用token.ThrowIfCancellationRequested())

我的新代码看起来像这样:

var tokenSource = new CancellationTokenSource();
try
{
    Task.Factory.StartNew(() =>
    {
        return MyStaticClass.DoStuff(tokenSource.Token);
    }, tokenSource.Token)
    .ContinueWith(task =>
    {
        var param = new object[1];
        param[0] = task.Result;
        // I need to use Invoke here because "DoStuffWith()" does UI stuff.
        Invoke(new MyDelegate(DoStuffWith, param));
    });
}
catch (OperationCanceledException)
{
    // Cancel gracefully.
}

然而，OperationCanceledException从未被捕获。这是怎么呢我把我的try/catch块放在哪里?

Task.Factory.StartNew(() =>
{
    // The task
}, tokenSource.Token)
.ContinueWith(task =>
{
    // The normal stuff
}, TaskContinuationOptions.OnlyOnRanToCompletion)
.ContinueWith(task =>
{
    // Handle cancellation
}, TaskContinuationOptions.OnlyOnCanceled)
.ContinueWith(task =>
{
    // Handle other exceptions
}, TaskContinuationOptions.OnlyOnFaulted);

Task.Factory.StartNew(() =>
{
    // The task
}, tokenSource.Token)
.ContinueWith(task =>
{
    switch (task.Status)
    {
    case TaskStatus.RanToCompletion:
        // The normal stuff
        break;
    case TaskStatus.Canceled:
        // Handle cancellation
        break;
    case TaskStatus.Faulted:
        // Handle other exceptions
        break;
    }
});