/// <summary>
 /// Get the request stream
 /// </summary>
 /// <param name="request">The request</param>
 /// <returns>The Request stream</returns>
 private Task <Stream> GetWebRequestStream(IEwsHttpWebRequest request)
 {
     // In the async case, although we can use async callback to make the entire worflow completely async,
     // there is little perf gain with this approach because of EWS's message nature.
     // The overall latency of BeginGetRequestStream() is same as GetRequestStream() in this case.
     // The overhead to implement a two-step async operation includes wait handle synchronization, exception handling and wrapping.
     // Therefore, we only leverage BeginGetResponse() and EndGetResponse() to provide the async functionality.
     // Reference: http://www.wintellect.com/CS/blogs/jeffreyr/archive/2009/02/08/httpwebrequest-its-request-stream-and-sending-data-in-chunks.aspx
     return(request.GetRequestStream());
 }
        /// <summary>
        /// Executes this instance.
        /// </summary>
        /// <returns></returns>
        internal AutodiscoverResponse InternalExecute()
        {
            this.Validate();

            try
            {
                IEwsHttpWebRequest request = this.Service.PrepareHttpWebRequestForUrl(this.Url);

                this.Service.TraceHttpRequestHeaders(TraceFlags.AutodiscoverRequestHttpHeaders, request);

                bool needSignature = this.Service.Credentials != null && this.Service.Credentials.NeedSignature;
                bool needTrace     = this.Service.IsTraceEnabledFor(TraceFlags.AutodiscoverRequest);

                using (Stream requestStream = request.GetRequestStream())
                {
                    using (MemoryStream memoryStream = new MemoryStream())
                    {
                        using (EwsServiceXmlWriter writer = new EwsServiceXmlWriter(this.Service, memoryStream))
                        {
                            writer.RequireWSSecurityUtilityNamespace = needSignature;
                            this.WriteSoapRequest(
                                this.Url,
                                writer);
                        }

                        if (needSignature)
                        {
                            this.service.Credentials.Sign(memoryStream);
                        }

                        if (needTrace)
                        {
                            memoryStream.Position = 0;
                            this.Service.TraceXml(TraceFlags.AutodiscoverRequest, memoryStream);
                        }

                        EwsUtilities.CopyStream(memoryStream, requestStream);
                    }
                }

                using (IEwsHttpWebResponse webResponse = request.GetResponse())
                {
                    if (AutodiscoverRequest.IsRedirectionResponse(webResponse))
                    {
                        AutodiscoverResponse response = this.CreateRedirectionResponse(webResponse);
                        if (response != null)
                        {
                            return(response);
                        }
                        else
                        {
                            throw new ServiceRemoteException(Strings.InvalidRedirectionResponseReturned);
                        }
                    }

                    using (Stream responseStream = AutodiscoverRequest.GetResponseStream(webResponse))
                    {
                        using (MemoryStream memoryStream = new MemoryStream())
                        {
                            // Copy response stream to in-memory stream and reset to start
                            EwsUtilities.CopyStream(responseStream, memoryStream);
                            memoryStream.Position = 0;

                            this.Service.TraceResponse(webResponse, memoryStream);

                            EwsXmlReader ewsXmlReader = new EwsXmlReader(memoryStream);

                            // WCF may not generate an XML declaration.
                            ewsXmlReader.Read();
                            if (ewsXmlReader.NodeType == XmlNodeType.XmlDeclaration)
                            {
                                ewsXmlReader.ReadStartElement(XmlNamespace.Soap, XmlElementNames.SOAPEnvelopeElementName);
                            }
                            else if ((ewsXmlReader.NodeType != XmlNodeType.Element) || (ewsXmlReader.LocalName != XmlElementNames.SOAPEnvelopeElementName) || (ewsXmlReader.NamespaceUri != EwsUtilities.GetNamespaceUri(XmlNamespace.Soap)))
                            {
                                throw new ServiceXmlDeserializationException(Strings.InvalidAutodiscoverServiceResponse);
                            }

                            this.ReadSoapHeaders(ewsXmlReader);

                            AutodiscoverResponse response = this.ReadSoapBody(ewsXmlReader);

                            ewsXmlReader.ReadEndElement(XmlNamespace.Soap, XmlElementNames.SOAPEnvelopeElementName);

                            if (response.ErrorCode == AutodiscoverErrorCode.NoError)
                            {
                                return(response);
                            }
                            else
                            {
                                throw new AutodiscoverResponseException(response.ErrorCode, response.ErrorMessage);
                            }
                        }
                    }
                }
            }
            catch (WebException ex)
            {
                if (ex.Status == WebExceptionStatus.ProtocolError && ex.Response != null)
                {
                    IEwsHttpWebResponse httpWebResponse = this.Service.HttpWebRequestFactory.CreateExceptionResponse(ex);

                    if (AutodiscoverRequest.IsRedirectionResponse(httpWebResponse))
                    {
                        this.Service.ProcessHttpResponseHeaders(
                            TraceFlags.AutodiscoverResponseHttpHeaders,
                            httpWebResponse);

                        AutodiscoverResponse response = this.CreateRedirectionResponse(httpWebResponse);
                        if (response != null)
                        {
                            return(response);
                        }
                    }
                    else
                    {
                        this.ProcessWebException(ex);
                    }
                }

                // Wrap exception if the above code block didn't throw
                throw new ServiceRequestException(string.Format(Strings.ServiceRequestFailed, ex.Message), ex);
            }
            catch (XmlException ex)
            {
                this.Service.TraceMessage(
                    TraceFlags.AutodiscoverConfiguration,
                    string.Format("XML parsing error: {0}", ex.Message));

                // Wrap exception
                throw new ServiceRequestException(string.Format(Strings.ServiceRequestFailed, ex.Message), ex);
            }
            catch (IOException ex)
            {
                this.Service.TraceMessage(
                    TraceFlags.AutodiscoverConfiguration,
                    string.Format("I/O error: {0}", ex.Message));

                // Wrap exception
                throw new ServiceRequestException(string.Format(Strings.ServiceRequestFailed, ex.Message), ex);
            }
        }