如何延迟“热"任务以使它们能够按固定顺序进行处理 [英] How to delay 'hot' tasks so they can processed in a set order

问题描述

说我有一系列任务:

        var task1 = DoThisAsync(...);
        var task2 = DoThatAsync(...);
        var task3 = DoOtherAsync(...);
        var taskN...

我正在寻找一种顺序处理一组任务的方法(由包含集合中的位置确定)，但是要让任务仅在轮到他们时才运行/开始，而不是在之前-并把所有这些都包装好完成自己的任务.

I am looking for a way to process a set of tasks in order (determined by place in containing collection say), but to have the tasks only run/start when its their turn and not before - and have all of that wrapped up in its own task.

问题约束/详细信息是:

Problem constraints / details are:

1. 这些任务需要按照一定的顺序执行，即task1，task2，...
2. 上一个任务必须异步完成，下一个任务才能开始
3. 任务数是可变的
4. 每次运行代码时，可能会指定一组不同的任务
5. 任务的顺序和数量是预先知道的.

主要问题是，只要我调用相关方法(如DoThis()...)以返回每个任务，该任务就已经热"或正在运行，违反了上面的(2).

The main problem is that as soon as I call the relevant method (like DoThis()...) to return each task, that task is already 'hot' or running, violating (2) above.

我曾经尝试过使用.ContinueWith(..)，但是如果我像上面那样调用每个任务来设置延续，或者将它们添加到列表或集合中，它们就已经开始了.

I have tried working with.ContinueWith(..) , but if I call each of tasks like above to set the continuations or add them to a list or collection they've already started.

不确定是否懒惰< T>可能有帮助，但目前看不到吗?

Not sure if Lazy < T > might help but can't see how at present?

希望这很有意义，因为我对异步/等待/任务还很陌生.

Hope this makes sense as I'm fairly new to async / await / tasks.

非常感谢.

推荐答案

调用方法将运行代码.如果您想要一个对象，该对象将调用此方法以后，请使用委托.

Calling a method runs code. If you want an object that will call this method later, then use a delegate.

在这种情况下，您可以使用Func<Task>，这是一个异步委托.这些列表就足够了:

In this case, you could use Func<Task>, which is an asynchronous delegate. A list of these should suffice:

// Build the list of operations in order.
var operations = new List<Func<Task>>();
operations.Add(() => DoThisAsync(...));
operations.Add(() => DoThatAsync(...));
operations.Add(() => DoOtherAsync(...));

// Execute them all one at a time.
foreach (var operation in operations)
  await operation();

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