C# TPL 数据流 - 完成不起作用

Question

此代码永远不会到达最后一行，因为完成不会从 saveBlock 传播到 sendBlock。我做错了什么？

var readGenerateBlock = new TransformBlock<int, int>(n =>
    {
        Console.WriteLine("Read " + n);
        Thread.Sleep(15);
        return n;
    }); 
var groupingBlock = new BatchBlock<int>(10);
var saveBlock = new TransformManyBlock<int[], int>(n =>
    {
        Console.WriteLine("Saving {0} items [{1}; {2}]", n.Count(), n.First(), n.Last());
        Thread.Sleep(150);
        return n;
    }); 
var sendBlock = new TransformBlock<int, int>(n =>
    {
        Console.WriteLine("Sending {0}", n);
        Thread.Sleep(25);
        return n;
    }, new ExecutionDataflowBlockOptions { MaxDegreeOfParallelism = 2 }); 

readGenerateBlock.LinkTo(groupingBlock, new DataflowLinkOptions { PropagateCompletion = true });
groupingBlock.LinkTo(saveBlock, new DataflowLinkOptions { PropagateCompletion = true });
saveBlock.LinkTo(sendBlock, new DataflowLinkOptions { PropagateCompletion = true });

Parallel.For(0, 250, i => readGenerateBlock.Post(i));
readGenerateBlock.Complete();

sendBlock.Completion.Wait();
Console.WriteLine("Completed.");

Answer 1

您必须先从块中读取数据才能完成。由于 noöne 正在阅读 saveBlock，它永远不会完成。

如果您不需要数据，最简单的解决方案是使用 ActionBlock 而不是 TransformBlock。否则，就一直读取数据，直到区块完成。