/// <summary>
        /// Sends a PROPFIND Http Request.
        /// </summary>
        /// <param name="cookies">The cookies returned from previously authenticating.</param>
        /// <param name="URI">The URI to send the request to.</param>
        /// <param name="depth">The value of the depth header.</param>
        /// <param name="content">XML content.</param>
        /// <returns>A Http Response.</returns>
        private static HttpWebResponse SendPropFindRequest(CookieCollection cookies,
                                                          string URI,
                                                          string depth,
                                                          string content)
        {
            IDictionary<string, string> headers = new Dictionary<string, string>();
            headers.Add("Depth", depth);
 
            return SendRequest(cookies, URI, "PROPFIND", headers, content);
        }
 
        /// <summary>
        /// Sends a Http Request with text/xml content.
        /// </summary>
        /// <param name="cookies">The cookies returned from previously authenticating.</param>
        /// <param name="URI">The URI to send the request to.</param>
        /// <param name="method">The request method to use.</param>
        /// <param name="headers">Optional Http request headers.</param>
        /// <param name="content">XML content.</param>
        /// <returns>A Http Response.</returns>
        private static HttpWebResponse SendRequest(CookieCollection cookies,
                                                   string URI,
                                                   string method,
                                                   IDictionary<string, string> headers,
                                                   string content)
        {
            byte[] bytes = null;
 
            if (content != null)
            {
                bytes = Encoding.UTF8.GetBytes(content);
            }
            return SendRequest(cookies, URI, method, "text/xml", headers, bytes);
        }
 
        /// <summary>
        /// Sends a Http Request to the URI.
        /// </summary>
        /// <param name="cookies">Cookies to be sent with the request (i.e. obtained from a previous logon).</param>
        /// <param name="URI">The URI to send the request to.</param>
        /// <param name="method">The request method.</param>
        /// <param name="contentType">The content type e.g. text/xml.</param>
        /// <param name="headers">Any additional headers to send.</param>
        /// <param name="content">The content to send.</param>
        /// <returns>A Http Response.</returns>
        private static HttpWebResponse SendRequest(CookieCollection cookies,
                                                   string URI,
                                                   string method,
                                                   string contentType,
                                                   IDictionary<string, string> headers,
                                                   byte[] content)
        {
            ServicePointManager.ServerCertificateValidationCallback += AllowAllSites;
 
            try
            {
                HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(URI);
 
                // Add cookies required for Outlook Web Access (OWA) Forms Authentication if there aren't any
                // then use the default credentials instead (i.e. the user that the service is running as)
                request.CookieContainer = new CookieContainer();
 
                if (cookies != null && cookies.Count > 0)
                {
                    request.CookieContainer.Add(cookies);
                }
                else
                {
                    request.UseDefaultCredentials = true;
                }
                request.Method = method;
                request.ContentType = contentType;
 
                // Add optional headers.
                if (headers != null)
                {
                    foreach (string key in headers.Keys)
                    {
                        request.Headers.Set(key, headers[key]);
                    }
                }
 
                // Add optional content
                if (content != null)
                {
                    request.ContentLength = content.Length;
 
                    using (Stream stream = request.GetRequestStream())
                    {
                        stream.Write(content, 0, content.Length);
                    }
                }
                return (HttpWebResponse)request.GetResponse();
            }
            finally
            {
                ServicePointManager.ServerCertificateValidationCallback -= AllowAllSites;
            }
        }
 
        /// <summary>
        /// Used to accept all certificates.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="certificate"></param>
        /// <param name="chain"></param>
        /// <param name="errors"></param>
        /// <returns>true</returns>
        private static Boolean AllowAllSites(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors errors)
        {
            return true;
        }