c# - 如何在不阻塞 UI 的情况下顺序运行多个任务？

Question

我试图按顺序运行这些任务，而不会在 UI 中出现任何阻塞，但是，我已经测试了我找到的所有方法，但仍然遇到问题，当我让任务在没有 UI 阻塞的情况下运行时，我任务中缺少步骤或某些任务无限运行。

 public void StartAsync(CancellationToken cancellationToken, string path, int i)
    
    {
        var task1 = Task.Run(() => Task1(path, step, i)); // 
        var task2 = Task.Run(() => Task2(cancellationToken)); // wait for task1 to complete
        var task3 = Task.Run(() => Task3(cancellationToken)); // wait for task2 to complete
        var task4 = Task.Run(() => Task4(cancellationToken, i)); // will call an external process ) ... wait for task3 to complete
        Task.WaitAll(task1, task2, task3, task4);
    }

 public void AnotherTask()
    
    {
        // Some other code ( will call an external process )
    }


 public void RunAllTasks()
    {
       int step = 5;
       cancellationToken = CancellationToken.None;
       string path = "...\\..";
       for (int i = 0;i<step;i++)
        {
             StartAsync(cancellationToken, string path, int i) 
        }

      // wait for StartAsync to complete
       AnotherTask();
    }

private void button_Click(object sender, RoutedEventArgs e) 
    {
        RunAllTasks();
    }

Answer 1

您应该像这样等待每个任务

public async Task StartAsync(CancellationToken cancellationToken, string path, int i)    
{
    await Task.Run(() => Task1(path, step, i)); 
    await Task.Run(() => Task2(cancellationToken));
    await Task.Run(() => Task3(cancellationToken));
    await Task.Run(() => Task4(cancellationToken, i));
}

或者也许只是在单个 Task.Run 操作中按顺序调用它们，例如

public Task StartAsync(CancellationToken cancellationToken, string path, int i)    
{
    return Task.Run(() =>
    {
        Task1(path, step, i); 
        Task2(cancellationToken);
        Task3(cancellationToken));
        Task4(cancellationToken, i);
    });
}

并等待 StartAsync 调用，例如

public async Task RunAllTasks()
{
     ...
     for (int i = 0;i < step; i++)
     {
         await StartAsync(cancellationToken, path, i);
     }
     ...
}

private async void button_Click(object sender, RoutedEventArgs e) 
{
    await RunAllTasks();
}

如果您想并行多次调用 StartAsync，类似这样的方法也可能有效:

await Task.WhenAll(Enumerable
    .Range(0, 5)
    .Select(i => StartAsync(cancellationToken, path, i)));