在 ForEach 循环中链接顺序异步任务：这是一个好方法吗？

Question

我正在开发一项 windows 服务，我有两个相互依赖的相关调用，我想运行异步地为每个 "pair" 或 "set" 的电话。有几种方法可以做到这一点，我尝试了几种不同的方法并解决了这个问题，因为处理一个代码块比处理两个单独的块有自己的 await Task.WhenAll() 调用更方便。在我的测试中，这似乎按预期工作，但我以前从未像这样将两个任务链接在一起，我想知道这是否是一个好方法，是否有更合适的方法来获得相同的结果（单个代码块）。

这是我的。这看起来是一种合理的任务链方式吗？如果不是，请告诉我原因。

提前致谢。 -弗兰克

//get all pending batches
foreach (string batchId in workload)
{
    try
    {
        // I am using this ContinueWith pattern here to aggregate the Tasks
        // which makes it more convenient to handle exceptions in one place
        Task t = bll.GetIncomingBatchAsync(batchId).ContinueWith(
            task => bll.SaveIncomingBatchAsync(task.Result),
            TaskContinuationOptions.OnlyOnRanToCompletion);

        saveBatchTasks.Add(t);
    }
    catch (Exception ex)
    {
        _logger.WriteError(ex, "ProcessWorkloadAsync error building saveBatchTasks!");
        throw ex;
    }
}

try
{
    await Task.WhenAll(saveBatchTasks);
}
catch (Exception ex)
{
    _logger.WriteError(ex, "ProcessWorkloadAsync error executing saveBatchTasks!");
    throw ex;
}

Answer 1

没有，you should not use ContinueWith。请改用 await。

如果您担心将两个函数的逻辑分开，只需使用本地函数即可：

//get all pending batches
foreach (string batchId in workload)
{
  try
  {
    async Task GetAndSave()
    {
      var result = await bll.GetIncomingBatchAsync(batchId);
      await bll.SaveIncomingBatchAsync(result);
    }

    saveBatchTasks.Add(GetAndSave());
  }
  catch (Exception ex)
  {
    _logger.WriteError(ex, "ProcessWorkloadAsync error building saveBatchTasks!");
    throw ex;
  }
}

Answer 2

通常结合老式 ContinueWith method with async/await is not recommended, since the later was invented to replace the former. You could use LINQ 在一行中创建任务，如果您愿意：

Task[] saveBatchTasks = workload.Select(async batchId =>
{
    var result = await bll.GetIncomingBatchAsync(batchId);
    await bll.SaveIncomingBatchAsync(result);
}).ToArray();

await Task.WhenAll(saveBatchTasks);

在 ForEach 循环中链接顺序异步任务：这是一个好方法吗？

Chaining sequential async tasks within a ForEach loop: Is this a good way to do it?

c#

asynchronous

async-await

task-parallel-library

continuewith