vedhæft fil til mail

jeg kan sende en mail via HttpWebRequest det virker fint, men jeg vil også gerne kunne vedhæfte en fil til min mail hvordan gør jeg det har forsøgt mig med dette herunder... Men når jeg så åbner filen indeholder den bare BODY....
Mangler at vedhæfte selve filen, er der nogle der kan hjælpe med det?


string strServer = "192.168.125.4";
        string strSenderAlias = "min";
        string strFrom = "min@email.dk";
        string strTo = "min@andenEmail.dk";
        string strSubject = "Send via HttpWebRequest";
        string strBody = "Hello World";

        string sUri;
        sUri = "http://" + strServer + "/Exchange/" + strSenderAlias;
        sUri = sUri + "/%23%23DavMailSubmissionURI%23%23/";

        System.Uri myUri = new System.Uri(sUri);
        HttpWebRequest HttpWRequest = (HttpWebRequest)WebRequest.Create(myUri);

        string sQuery;
        DateTime mySentTime = new DateTime();
        sQuery = "From: " + strFrom + "\n" +
          "To: " + strTo + "\n" +
          "Subject: " + strSubject + "\n" +
          "Content-Disposition: attachment;" + "\n" +
          " filename = setupxlg.txt" + "\n" +
          "Date: " + DateTime.Now.ToString() + "\n" +
          "X-Mailer: My DAV mailer" + "\n" +
          "MIME-Version: 1.0" + "\n" +
          "Content-Type: text/plain;" + "\n" +         
          "Charset = \"iso-8859-1\"" + "\n" +
          "Content-Transfer-Encoding: 7bit" + "\n" + "\n" +
          strBody;


NetworkCredential myCred = new NetworkCredential(@"sonwin\min", "min005");
        CredentialCache myCredentialCache = new CredentialCache();
        myCredentialCache.Add(myUri, "Basic", myCred);
        HttpWRequest.Credentials = myCredentialCache;

        // Set the headers.
        HttpWRequest.Headers.Set("Translate", "f");
        HttpWRequest.ContentType = "message/rfc822";
        HttpWRequest.ContentLength = sQuery.Length;

        //Set the request timeout to 5 minutes.
        HttpWRequest.Timeout = 300000;
        // Set the request method.
        HttpWRequest.Method = "PUT";



        // Store the data in a byte array.
        byte[] ByteQuery = System.Text.Encoding.ASCII.GetBytes(sQuery);
        HttpWRequest.ContentLength = ByteQuery.Length;
        Stream QueryStream = HttpWRequest.GetRequestStream();
        // write the data to be posted to the Request Stream
        QueryStream.Write(ByteQuery, 0, ByteQuery.Length);
        QueryStream.Close();


        // Send the request and get the response.
        HttpWebResponse HttpWResponse = (HttpWebResponse)HttpWRequest.GetResponse();

        // Get the Status code.
        int iStatCode = (int)HttpWResponse.StatusCode;
        string sStatus = iStatCode.ToString();
        Console.WriteLine("Status Code: {0}", sStatus);
        // Get the request headers.
        string sReqHeaders = HttpWRequest.Headers.ToString();
        Console.WriteLine(sReqHeaders);