Async HttpWebRequest failing to fetch all range requests

I'm attempting to fetch a URI in parts by setting the Range header on my HttpWebRequest, and then requesting them asynchronously using Begin/EndGetResponse :

using System;
using System.Net;

namespace MultiGet
{
    class Program
    {        
        static void GetterCallback(IAsyncResult ip)
        {
            try
            {
                var req = (HttpWebRequest)ip.AsyncState;
                var response = req.EndGetResponse(ip);
                Console.WriteLine("In GetterCallback {0}",req.Headers["Range"]);
                response.Close();
            }
            catch
            {
                Console.WriteLine("Exception Thrown");
            }
        }

        static void Main(string[] args)
        {
            string URI = "http://www.microsoft.com";
            var req = (HttpWebRequest)WebRequest.Create(URI);
            req.Method = WebRequestMethods.Http.Head;
            var response = req.GetResponse();
            int TotalSize = Int32.Parse(response.Headers["Content-Length"]);

            Console.WriteLine("URI Content-Length {0}",TotalSize);
            Console.WriteLine("Now requesting the URI in 10 parts");                        

            Int32 start = 0;
            var splitreq = new HttpWebRequest[10];
            var results = new IAsyncResult[10];
            for (int i = 0; i < 10; i++)
            {
                Int32 end = start + TotalSize / 10 - 1;
                if (i == 9) end = TotalSize;

                splitreq[i] = (HttpWeb开发者_开发百科Request)WebRequest.Create(URI);
                splitreq[i].AddRange(start, end);             

                results[i] = splitreq[i].BeginGetResponse(new AsyncCallback(GetterCallback), splitreq[i]);

                start = end + 1;
            }
            Console.ReadKey(true);

            //This shows that some async calls did not complete
            foreach (var result in results)
            {
                Console.WriteLine(result.IsCompleted);                
            }

        }

    }
}

Even if I wait for a long time (no keypress for the Console.ReadKey(true)), allrequests do not complete. I'm not sure where I'm going wrong.

One possible problem is that you're not using using statements for the responses, so it's possible that they're holding onto HTTP connections in the pool.

So for example, I suggest you change your callback to:

static void GetterCallback(IAsyncResult ip)
{
    try
    {
        var req = (HttpWebRequest)ip.AsyncState;
        using (var response = req.EndGetResponse(ip))
        {
            Console.WriteLine("In GetterCallback {0}",req.Headers["Range"]);
        }
    }
    catch
    {
        Console.WriteLine("Exception Thrown");
    }
}

And earlier in your program, when you're finding the content length:

int TotalSize;
using (var response = (HttpWebResponse) req.GetResponse())
{                
    TotalSize = (int)response.ContentLength;
}

When you've made those changes, try it again... it's certainly working for me.