public static class WebRequestExtensions

    {

        public static HttpWebRequest CloneRequest(this HttpWebRequest originalRequest, Uri newUri)

        {

            return CloneHttpWebRequest(originalRequest, newUri);

        }

        public static WebRequest CloneRequest(this WebRequest originalRequest, Uri newUri)

        {

            var httpWebRequest = originalRequest as HttpWebRequest;

            if (httpWebRequest != null) return CloneHttpWebRequest(httpWebRequest, newUri);

            return CloneWebRequest(originalRequest, newUri);

        }

        private static HttpWebRequest CloneHttpWebRequest(HttpWebRequest old, Uri newUri)

        {

            var @new = (HttpWebRequest) WebRequest.Create(newUri);

            CopyWebRequestProperties(old, @new);

            CopyHttpWebRequestProperties(old, @new);

            CopyHttpWebRequestHeaders(old, @new);

            return @new;

        }

        private static WebRequest CloneWebRequest(WebRequest old, Uri newUri)

        {

            var @new = WebRequest.Create(newUri);

            CopyWebRequestProperties(old, @new);

            CopyWebRequestHeaders(old, @new);

            return @new;

        }

        private static void CopyWebRequestProperties(WebRequest old, WebRequest @new)

        {

            @new.AuthenticationLevel = old.AuthenticationLevel;

            @new.CachePolicy = old.CachePolicy;

            @new.ConnectionGroupName = old.ConnectionGroupName;

            @new.ContentType = old.ContentType;

            @new.Credentials = old.Credentials;

            @new.ImpersonationLevel = old.ImpersonationLevel;

            @new.Method = old.Method;

            @new.PreAuthenticate = old.PreAuthenticate;

            @new.Proxy = old.Proxy;

            @new.Timeout = old.Timeout;

            @new.UseDefaultCredentials = old.UseDefaultCredentials;

            if (old.ContentLength > ) @new.ContentLength = old.ContentLength;

        }

        private static void CopyWebRequestHeaders(WebRequest old, WebRequest @new)

        {

            string[] allKeys = old.Headers.AllKeys;

            foreach (var key in allKeys)

            {

                @new.Headers[key] = old.Headers[key];

            }

        }

        private static void CopyHttpWebRequestProperties(HttpWebRequest old, HttpWebRequest @new)

        {

            @new.Accept = old.Accept;

            @new.AllowAutoRedirect = old.AllowAutoRedirect;

            @new.AllowWriteStreamBuffering = old.AllowWriteStreamBuffering;

            @new.AutomaticDecompression = old.AutomaticDecompression;

            @new.ClientCertificates = old.ClientCertificates;

            @new.SendChunked = old.SendChunked;

            @new.TransferEncoding = old.TransferEncoding;

            @new.Connection = old.Connection;

            @new.ContentType = old.ContentType;

            @new.ContinueDelegate = old.ContinueDelegate;

            @new.CookieContainer = old.CookieContainer;

            @new.Date = old.Date;

            @new.Expect = old.Expect;

            @new.Host = old.Host;

            @new.IfModifiedSince = old.IfModifiedSince;

            @new.KeepAlive = old.KeepAlive;

            @new.MaximumAutomaticRedirections = old.MaximumAutomaticRedirections;

            @new.MaximumResponseHeadersLength = old.MaximumResponseHeadersLength;

            @new.MediaType = old.MediaType;

            @new.Pipelined = old.Pipelined;

            @new.ProtocolVersion = old.ProtocolVersion;

            @new.ReadWriteTimeout = old.ReadWriteTimeout;

            @new.Referer = old.Referer;

            @new.Timeout = old.Timeout;

            @new.UnsafeAuthenticatedConnectionSharing = old.UnsafeAuthenticatedConnectionSharing;

            @new.UserAgent = old.UserAgent;

        }

        private static void CopyHttpWebRequestHeaders(HttpWebRequest old, HttpWebRequest @new)

        {

            var allKeys = old.Headers.AllKeys;

            foreach (var key in allKeys)

            {

                switch (key.ToLower(CultureInfo.InvariantCulture))

                {

                    // Skip all these reserved headers because we have to set them through properties

                    case "accept":

                    case "connection":

                    case "content-length":

                    case "content-type":

                    case "date":

                    case "expect":

                    case "host":

                    case "if-modified-since":

                    case "range":

                    case "referer":

                    case "transfer-encoding":

                    case "user-agent":

                    case "proxy-connection":

                        break;

                    default:

                        @new.Headers[key] = old.Headers[key];

                        break;

                }

            }

        }

    }