/// <summary>
        /// Encode common part of DigestValidationRequest
        /// </summary>
        /// <param name="serverName">server name</param>
        /// <param name="domainName">domain name</param>
        /// <param name="accountName">account name</param>
        /// <param name="digestType">digest type</param>
        /// <param name="digestChallengeAlgorithm">digest challenge algorithm</param>
        /// <param name="dpspResponse">dpspResponse</param>
        /// <param name="payload">DIGEST_VALIDATION_REQ_Payload structure</param>
        /// <param name="digestValidationReq">digestValidationReq</param>
        private static void EncodeCommonPartOfDigestValidationRequest(
            string serverName,
            string domainName,
            string accountName,
            DigestType_Values digestType,
            string digestChallengeAlgorithm,
            DpspResponse dpspResponse,
            ref DIGEST_VALIDATION_REQ_Payload payload,
            ref DIGEST_VALIDATION_REQ digestValidationReq
            )
        {
            digestValidationReq.MessageType = DIGEST_VALIDATION_REQ_MessageType_Values.Default;
            digestValidationReq.Version = DIGEST_VALIDATION_REQ_Version_Values.Default;
            digestValidationReq.DigestType = digestType;
            digestValidationReq = SetQopType(dpspResponse, digestValidationReq);
            digestValidationReq = SetAlgType(digestChallengeAlgorithm, digestValidationReq);
            digestValidationReq.CharsetType = CharsetType_Values.UTF8;
            digestValidationReq.NameFormat = NameFormat_Values.None;
            digestValidationReq.Flags =
                DIGEST_VALIDATION_FLAGS.FormatOfUserNameAndRealmIsDeterminedByDC
                | DIGEST_VALIDATION_FLAGS.RequestIsSentFromServer;

            digestValidationReq.Reserved3 = DIGEST_VALIDATION_REQ_Reserved3_Values.Default;
            digestValidationReq.Reserved4 = Reserved4_Values.Default;
            digestValidationReq.Pad1 = DIGEST_VALIDATION_REQ_Pad1_Values.Default;

            // Each of the strings MUST be included. If the string value is empty,
            // then a terminating null character MUST be used for the value.
            payload.Username = dpspResponse.GetAttributeValue(DpspUtility.USER_NAME_DIRECTIVE);
            payload.Realm = dpspResponse.GetAttributeValue(DpspUtility.REALM_DIRECTIVE);
            payload.Nonce = dpspResponse.GetAttributeValue(DpspUtility.NONCE_DIRECTIVE);
            payload.CNonce = dpspResponse.GetAttributeValue(DpspUtility.CNONCE_DIRECTIVE);
            payload.NonceCount = dpspResponse.GetAttributeValue(DpspUtility.NONCE_COUNT_DIRECTIVE);
            payload.QOP = dpspResponse.GetAttributeValue(DpspUtility.MESSAGE_QOP_DIRECTIVE);
            payload.Response = dpspResponse.GetAttributeValue(DpspUtility.RESPONSE_DIRECTIVE);

            payload.AccountName = accountName; ;
            payload.ServerName = serverName;
            payload.Domain = domainName;
        }
        /// <summary>
        /// Construct DIGEST_VALIDATION_REQ structure
        /// </summary>
        /// <param name="serverName">server name</param>
        /// <param name="domainName">domain name</param>
        /// <param name="accountName">account name</param>
        /// <param name="httpMethod">http method</param>
        /// <param name="digestType">digest type</param>
        /// <param name="digestChallengeAlgorithm">digest challenge algorithm</param>
        /// <param name="dpspResponse">dpspResponse class instance</param>
        /// <returns>DIGEST_VALIDATION_REQ structure</returns>
        /// <exception cref="ArgumentNullException">
        /// Thrown when dpspResponse or httpMethod is null  
        /// </exception>
        /// <exception cref="ArgumentException">
        /// Thrown when httpMethod or digestType input is invalid
        /// </exception>        
        public static DIGEST_VALIDATION_REQ CreateDigestValidationRequestPacket(
            string serverName,
            string domainName,
            string accountName,
            string httpMethod,
            DigestType_Values digestType,
            string digestChallengeAlgorithm,
            DpspResponse dpspResponse)
        {
            if (dpspResponse == null)
            {
                throw new ArgumentNullException("dpspResponse");
            }

            if (httpMethod == null)
            {
                throw new ArgumentNullException("httpMethod");
            }

            DIGEST_VALIDATION_REQ_Payload payload = new DIGEST_VALIDATION_REQ_Payload();

            DIGEST_VALIDATION_REQ digestValidationReq = new DIGEST_VALIDATION_REQ();
            if (digestType == DigestType_Values.Basic)
            {
                EncodeCommonPartOfDigestValidationRequest(
                    serverName,
                    domainName,
                    accountName,
                    digestType,
                    digestChallengeAlgorithm,
                    dpspResponse,
                    ref payload,
                    ref digestValidationReq);

                payload.Algorithm = dpspResponse.GetAttributeValue(DpspUtility.ALGORITHM_DIRECTIVE);
                payload.URI = dpspResponse.GetAttributeValue(DpspUtility.BASIC_DIGEST_URI_DIRECTIVE);
                if (httpMethod.ToUpper().Equals(HTTP_GET) || httpMethod.ToLower().Equals(HTTP_PUT))
                {
                    payload.Method = httpMethod;
                }
                else
                {
                    throw new ArgumentException("invalid http method", "httpMethod");
                }
            }
            else if (digestType == DigestType_Values.SASL)
            {
                EncodeCommonPartOfDigestValidationRequest(
                   serverName,
                   domainName,
                   accountName,
                   digestType,
                   digestChallengeAlgorithm,
                   dpspResponse,
                   ref payload,
                   ref digestValidationReq);

                payload.Method = SASL_AUTHENTICATE;
                payload.URI = dpspResponse.GetAttributeValue(DpspUtility.SASL_DIGEST_URI_DIRECTIVE);
                payload.Authzid = dpspResponse.GetAttributeValue(DpspUtility.AUTHZID_DIRECTIVE);
                payload.Hentity = dpspResponse.GetAttributeValue(DpspUtility.HENTITY_DIRECTIVE);

            }
            else
            {
                throw new ArgumentException(
                    "invalid digestType value",
                    "digestType");
            }

            digestValidationReq.Payload = payload.GetBytes();
            digestValidationReq = UpdatePacketInfo(digestValidationReq);

            return digestValidationReq;
        }