半并行运行多个任务

Question

我有一个任务列表，其中每个任务都有两个子任务。 我只想在上一个任务完成第一个子任务后开始下一个任务。 （第一个子任务对单个 http api 调用大约 1000 次，如果我称之为“太多”，它似乎会下降，第二个任务是一个相当长时间运行的 cpu 绑定任务）。

我的想法类似于以下示例代码（在实际情况下，任务列表增长到至少 300 个）：

class Program
{
    

    static async Task Main(string[] args)
    {
        var test = new TestMultiTask();
        await test.TestListOfTasks();
        Console.WriteLine("Finished");
        Console.ReadLine();
    }
} 

public class TestMultiTask
{
    public List<Task> Tasks { get; private set; }
    public async Task TestListOfTasks()
    {
        Tasks = new List<Task>();
        Tasks.Add(Task2SubTask(new Progress<MyProgress>(ReportProgress), 0));
        await Task.WhenAll(Tasks);
        Console.WriteLine("Finished TestListOfTasks");
    }

    private void ReportProgress(MyProgress obj)
    {
        if (obj.ProgressNo < 10)
        {
            Tasks.Add(Task2SubTask(new Progress<MyProgress>(ReportProgress), obj.ProgressNo + 1));
        }
    }

    private async Task Task2SubTask(IProgress<MyProgress> progress, int i)
    {
        Console.WriteLine($"Task {i}, started.");
        await Task.Delay(700); // simulating getting data from web api (abt- 1000 calls)
        Console.WriteLine($"Task {i}, completed subtask 1."); 
        progress.Report(new MyProgress() { Task1Done = true, ProgressNo = i }); // now the next task can start getting data form web api.
        await Task.Run(() => Task.Delay(1000)); // Process the data collected (in this task) from the web api
        Console.WriteLine($"Task {i} done."); // return processed data.
    }

}

然而，这至少有一个缺陷 - Program.Main在列表中的第一个任务完成后立即继续，即使列表已扩展。 有谁知道这样做的更聪明的方法？ （也许是一种完全不同的方法？）

编辑：感谢您的评论..现在我尝试对代码进行评论以使其更加清晰。

Answer 1

首先，感谢许多评论。 我尝试了@Evk 的提议并最终得到了以下代码......

public class TestMultiTask2
{
    public List<Task> Tasks { get; private set; }
    public async Task TestListOfTasks()
    {
        var workers = new List<Worker>();
        var crunchingTasks = new List<Task>();
        var n = 10;
        for (int i = 0; i < n; i++)
        {
            var w = new Worker(i);
            workers.Add(w);
            await w.GetDataAsync(new Progress<MyProgress>(ReportProgress));
            crunchingTasks.Add(w.CrunchData(new Progress<MyProgress>(ReportProgress)));
        }
        await Task.WhenAll(crunchingTasks);
        Console.WriteLine($"Worker 0 data: {string.Join(", ", workers[0].Datas)}");
        Console.WriteLine($"Worker {n-1} data: {string.Join(", ", workers[n-1].Datas)}");
        Console.WriteLine("Finished TestListOfTasks");
    }

    private void ReportProgress(MyProgress obj)
    {
        if (obj.Task2Started)
        {
            Console.WriteLine($"Task no. {obj.TaskNo} has started chrunching data: {obj.Task2Started}");
        }
        else if(obj.Task2Done)
        {
            Console.WriteLine($"Task no. {obj.TaskNo} has finished chrunching data: {obj.Task2Done}");
        }
        else if (obj.Task1Done)
        {
            Console.WriteLine($"Task no. {obj.TaskNo} has finished getting data: {obj.Task1Done}"); 
        }
    }


}

public class MyProgress
{
    public int TaskNo { get; set; }
    public bool Task1Done { get; set; }
    public bool Task2Done { get; internal set; }
    public bool Task2Started { get; internal set; }
}

public class Worker
{
    public int ID { get; set; }

    public Worker(int id)
    {
        ID = id;
    }
    public List<int> Datas { get; set; } = new List<int>() { 0, 0, 0 };
    public async Task GetDataAsync(IProgress<MyProgress> progress)
    {
        await Task.Delay(500);
        Datas = new List<int>() { 1, 2, 3 };
        progress.Report(new MyProgress() { TaskNo = ID, Task1Done = true });
    }

    public async Task CrunchData(IProgress<MyProgress> progress)
    {
        progress.Report(new MyProgress() { TaskNo = ID, Task2Started = true });
        await Task.Run(async () => { await Task.Delay(5000); Datas.Reverse(); });
        progress.Report(new MyProgress() { TaskNo = ID, Task2Done = true });
    }
}
class Program
{


    static async Task Main(string[] args)
    {
        var test = new TestMultiTask2();
        await test.TestListOfTasks();
        Console.WriteLine("Finished");
        Console.ReadLine();
    }
}