C＃DataFlow：等待ConcurrentExclusiveSchedulerPair启动的所有任务完成

Question

I have a list of operations to be executed, and can be cancelled on user interaction. Pretty simple, but ConcurrentExclusiveSchedulerPair .Completion is never finishing. Here's an example:

static void Main(string[] args)
{
    var taskSchedulerPair = new ConcurrentExclusiveSchedulerPair();
    var cts = new CancellationTokenSource();
    var optiions = new ExecutionDataflowBlockOptions
    {
        TaskScheduler = taskSchedulerPair.ConcurrentScheduler,
        CancellationToken = cts.Token,
        MaxDegreeOfParallelism = 5
    };
    var a1 = new ActionBlock<int>(new Func<int, Task<int>>(Moo), optiions);
    for (var i = 0; i < 20; i++) a1.Post(i);
    Console.WriteLine("Press any key to cancel...");
    Console.ReadKey(false);
    Console.WriteLine("Cancelling...");
    cts.Cancel();
    // taskSchedulerPair.Complete();
    taskSchedulerPair.Completion.Wait();
    // This never prints
    Console.WriteLine("Done.");
    Console.ReadKey(false);
}

public static async Task<int> Moo(int ms)
{
    Console.WriteLine("Starting: " + ms);
    await Task.Delay(4000);
    Console.WriteLine("Ending" + ms);
    return ms + 100;
}

Answer 1

From the docs

Calling Complete is optional. It is necessary only if you're relying on the Completion property for notification that all processing has been complete .

So if you want to Wait on the Completion property then you have to call Complete() on the scheduler. This behavior is the same for a data flow block; to rely on the Completion property you have to call Complete() on the block.