gistfile1.txt

    public static class ConcurrentCollectionExtensions
    {
        private const int MaxDegreeOfConcurrency = 10;

        /// <summary>
        /// Concurrently perform a task on each member of a collection
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="collection">The collection upon which each task should be performed</param>
        /// <param name="concurrentTask">The task to perform</param>
        /// <param name="maxDegreeOfConcurrency">The maximum number of concurrent operations</param>
        /// <returns></returns>
        public static async Task ConcurrentForEach<T>(this IEnumerable<T> collection, Func<T, Task> concurrentTask, int maxDegreeOfConcurrency = MaxDegreeOfConcurrency)
        {
            var semaphore = new SemaphoreSlim(maxDegreeOfConcurrency);
            var tasks = collection.Select(async student =>
            {
                using (await semaphore.TakeAsync())
                    await concurrentTask(student);
            });
            await Task.WhenAll(tasks);
        }

    }


public static class SemaphoreSlimExtensions
    {
        public static async Task<IDisposable> TakeAsync(this SemaphoreSlim semaphore)
        {
            await semaphore.WaitAsync().ConfigureAwait(false);
            return new SemaphoreSlimKey(semaphore);
        }

        private sealed class SemaphoreSlimKey : IDisposable
        {
            private readonly SemaphoreSlim _semaphore;
            public SemaphoreSlimKey(SemaphoreSlim semaphore) { _semaphore = semaphore; }
            void IDisposable.Dispose() { _semaphore.Release(); }
        }
    }