Applying Backpressure (aka Throttling) in TPL Dataflow

ThrottledTplDataflowPipelne.cs

using System.Threading;
using System.Threading.Tasks.Dataflow;

class Pipeline<T>
{
    private readonly SemaphoreSlim _semaphore;
    private readonly BufferBlock<T> _buffer;

    Pipeline(Action<T> action, int capacity)
    {
        _semaphore = new SemaphoreSlim(capacity, capacity);
        _buffer = new BufferBlock<T>();

        var actionBlock = new ActionBlock<T>(t => {
            try
            {
                action(t);
            }
            finally
            {
                _semaphore.Release();
            }
        });

        _buffer.LinkTo(actionBlock);
    }

    void Post(T message)
    {
        _semaphore.Wait();
        _buffer.Post(message);
    }
}