C# async tasks in a queue or waiting list

async-await, c#, task-parallel-library, throttling

Solution

Actually, the tasks start as soon as you call `DoWork`; when you `await` them, you are finishing the tasks.

One option for throttling tasks is `SemaphoreSlim`, which you can use as such:

private SemaphoreSlim _mutex = new SemaphoreSlim(3);
public async Task DoWorkAsync()
{
  await _mutex.WaitAsync();
  try
  {
    ...
  }
  finally
  {
    _mutex.Release();
  }
}

Another option is to use an actual queue, like an `ActionBlock<T>`, which has built-in throttling support.

Problem

i have an async Task like this: ``` public async Task DoWork() { } ``` And i have at the moment a: ``` List<Task> tmp = new List<Task>(); ``` where i add the tasks. I start the tasks like this: ``` foreach (Task t in tmp) { await t; } ``` Now my Question: What`s the best way to start the tasks and only run 3 of them, at the same time (until the others are waiting)? I think i need something like a queue/waiting list? It should also be possible to add more tasks after the queue is started. I`am using .NET 4.5. Thank you for any suggestion

Original source