Tasks as monads.

MonadicTasks.cs

class Program
{
    public static void Main()
    {
        string urls = @"http://www.google.com/
http://www.microsoft.com/
http://www.github.com/
http://news.ycombinator.com/
http://stackoverflow.com/
http://www.logos.com/";
        using (TextReader reader = new StringReader(urls))
        {
            List<Task<string>> tasks = new List<Task<string>>();
            for (int i = 0; i < 2; i++)
            {
                // chain SelectMany calls together
                var median1 =
                    from uri in reader.ReadLineAsync()
                    from data in new WebClient().DownloadStringTaskAsync(new Uri(uri))
                    from lines in Task.FromResult(SplitIntoLines(data))
                    from sorted in Task.Factory.StartNew(() => { Array.Sort(lines); return lines; })
                    select sorted[sorted.Length / 2];
                tasks.Add(median1);

                // SelectMany followed by Select
                var median2 =
                    from uri in reader.ReadLineAsync()
                    from data in new WebClient().DownloadStringTaskAsync(new Uri(uri))
                    let lines = SplitIntoLines(data)
                    let sorted = lines.OrderBy(x => x).ToArray()
                    select sorted[sorted.Length / 2];
                tasks.Add(median2);

                // mix of SelectMany and Select (NOTE: Dispose is not called)
                var median3 =
                    from uri in reader.ReadLineAsync()
                    let req = WebRequest.Create(uri)
                    from resp in req.GetResponseAsync()
                    let stream = resp.GetResponseStream()
                    let streamReader = new StreamReader(stream)
                    from data in streamReader.ReadToEndAsync()
                    let lines = SplitIntoLines(data)
                    let sorted = lines.OrderBy(x => x).ToArray()
                    select sorted[sorted.Length / 2];
                tasks.Add(median3);
            }
            Task.WaitAll(tasks.ToArray());
            tasks.ForEach(t => Console.WriteLine(t.Result));
        }
    }

    public static string[] SplitIntoLines(string value)
    {
        return value.Split(new[] { '\n', '\r' }, StringSplitOptions.RemoveEmptyEntries);
    }
}

public static class TaskExtensions
{
    public static Task<TResult> Select<TInput, TResult>(this Task<TInput> task, Func<TInput, TResult> selector)
    {
        return task.ContinueWith(t => selector(t.Result));
    }

#if !CSHARP50
    public static Task<TResult> SelectMany<TInput, TIntermediate, TResult>(this Task<TInput> task, Func<TInput, Task<TIntermediate>> selector, Func<TInput, TIntermediate, TResult> resultSelector)
    {
        return task.ContinueWith(t => selector(t.Result))
            .Unwrap()
            .ContinueWith(t => resultSelector(task.Result, t.Result));
    }
#else
    public static async Task<TResult> SelectMany<TInput, TIntermediate, TResult>(this Task<TInput> task, Func<TInput, Task<TIntermediate>> selector, Func<TInput, TIntermediate, TResult> resultSelector)
    {
        TInput input = await task;
        TIntermediate intermediate = await selector(input);
        return resultSelector(input, intermediate);
    }
#endif
}