TPLDataflow.cs

using System;
using System.Linq;
using System.Net;
using System.Text.RegularExpressions;
using System.Threading.Tasks.Dataflow;

namespace TPLDataflow
{
    class Program
    {
        static void Main(string[] args)
        {
            PrintLinksFromMSDNAsync();
            Console.ReadLine();
        }

        public static void PrintLinksFromMSDNAsync()
        {
            var printUrl = new ActionBlock<string>(s => {
                Console.WriteLine(s);
            });

            var extractUrlFromMatch = new TransformBlock<Match, string>(match =>
            {
                return match.Groups[1].Value;
            });

            extractUrlFromMatch.LinkTo(printUrl);
            
            var getUrlMacthes = new TransformManyBlock<string, Match>(content => {
                var regex = "href\\s*=\\s*(?:\"(?<1>[^\"]*)\"|(?<1>\\S+))";
                var matches = Regex.Matches(content, regex);
                return matches.Cast<Match>();
            });

            getUrlMacthes.LinkTo(extractUrlFromMatch);

            var getPageContent = new TransformBlock<string, string>(async url => {
                return await new WebClient().DownloadStringTaskAsync(url);
            });

            getPageContent.LinkTo(getUrlMacthes);

            getPageContent.Post("http://msdn.microsoft.com/pt-br/");
        }
    }
}