Await multiple async Task while setting max running task at a time

Question

So I just started to try and understand async, Task, lambda and so on, and I am unable to get it to work like I want. With the code below I want for it to lock btnDoWebReque

Answer 1

I have created an extension method for this.

It can be used like this:

var tt = new List>()
{
    () => Thread.Sleep(300), //Thread.Sleep can be replaced by your own functionality, like calling the website
    () => Thread.Sleep(800),
    () => Thread.Sleep(250),
    () => Thread.Sleep(1000),
    () => Thread.Sleep(100),
    () => Thread.Sleep(200),
};
await tt.WhenAll(3); //this will let 3 threads run, if one ends, the next will start, untill all are finished.

The extention method:

public static class TaskExtension
{
    public static async Task WhenAll(this List> actions, int threadCount)
    {
        var _countdownEvent = new CountdownEvent(actions.Count);
        var _throttler = new SemaphoreSlim(threadCount);

        foreach (Func action in actions)
        {
            await _throttler.WaitAsync();

            Task.Run(async () =>
            {
                try
                {
                    await action();
                }
                finally
                {
                    _throttler.Release();
                    _countdownEvent.Signal();
                }
            });
        }

        _countdownEvent.Wait();
    }
}