Async Governor - SemphoreSlim

Parallel.Async.SemephoreSlim.cs

// using System.Threading.Tasks

const int MAX_DEGREE_OF_PARALLELISM = 2;
static SemaphoreSlim _semaphore = new SemaphoreSlim(MAX_DEGREE_OF_PARALLELISM);

async void Main()
{
	var tasks = Enumerable.Range(0, 10)
					.Select(i => ExecTask(i))
					.ToArray();
	
	await Task.WhenAll(tasks);
	
	Console.WriteLine("ALL DONE.");
}


async Task<int> ExecTask(int index)
{
	await _semaphore.WaitAsync();
	try
	{
		Console.WriteLine($"Task {index} starting.");
		await Task.Delay(1000);
		Console.WriteLine($"Task {index} done.");
		return index;
	}
	finally
	{
		_semaphore.Release();
	}
}

/**********
* Output  *
***********

Task 0 starting.
Task 1 starting.
Task 1 done.
Task 0 done.
Task 3 starting.
Task 2 starting.
Task 2 done.
Task 3 done.
Task 4 starting.
Task 5 starting.
Task 5 done.
Task 4 done.
Task 7 starting.
Task 6 starting.
Task 6 done.
Task 7 done.
Task 8 starting.
Task 9 starting.
Task 8 done.
Task 9 done.
ALL DONE.

*/