private imsx_POXEnvelopeType HandleReadResultRequest(imsx_RequestHeaderInfoType requestHeader, imsx_POXBodyType requestBody)
        {
            imsx_POXEnvelopeType response;
            var readRequest = requestBody.Item as readResultRequest ?? new readResultRequest();
            var readResponse = new readResultResponse();

            var result = ReadResult(readRequest.resultRecord.sourcedGUID.sourcedId);
            if (result.IsValid)
            {
                if (!result.Score.HasValue)
                {
                    // The score could exist, but not found. If the grade has not yet been set via a replaceResult operation
                    // or an existing grade has been deleted via a deleteResult operation, the TC should return a valid
                    // response with a present but empty textString element.   The TC should not return 0.0 to indicate a
                    // non-existent grade and the TC should not return a failure status when a grade does not exist.
                    // It should simply return an "empty" grade.
                    response = CreateSuccessResponse(requestHeader.imsx_messageIdentifier,
                        $"Score for {readRequest.resultRecord.sourcedGUID.sourcedId} is null");
                    readResponse.result = new ResultType {resultScore = new TextType()};
                    var cultureInfo = new CultureInfo("en");
                    readResponse.result.resultScore.language = cultureInfo.Name;
                    readResponse.result.resultScore.textString = string.Empty;
                }
                else
                {
                    // The score exists
                    response = CreateSuccessResponse(requestHeader.imsx_messageIdentifier,
                        $"Score for {readRequest.resultRecord.sourcedGUID.sourcedId} is read");
                    readResponse.result = new ResultType {resultScore = new TextType()};
                    var cultureInfo = new CultureInfo("en");
                    readResponse.result.resultScore.language = cultureInfo.Name;
                    readResponse.result.resultScore.textString = result.Score.Value.ToString(cultureInfo);
                }
            }
            else
            {
                // The score could not exist (invalid assignment or user)
                response = CreateCustomResponse(requestHeader.imsx_messageIdentifier,
                    $"Invalid score sourcedId {readRequest.resultRecord.sourcedGUID.sourcedId}",
                    imsx_CodeMajorType.failure);
            }
            response.imsx_POXBody.Item = readResponse;
            return response;
        }
        private imsx_POXEnvelopeType HandleReplaceResultRequest(imsx_RequestHeaderInfoType requestHeader, imsx_POXBodyType requestBody)
        {
            imsx_POXEnvelopeType response;
            var replaceRequest = requestBody.Item as replaceResultRequest ?? new replaceResultRequest();

            var result = GetResult(replaceRequest.resultRecord);
            if (!result.Score.HasValue)
            {
                response = CreateCustomResponse(requestHeader.imsx_messageIdentifier,
                    "Invalid result",
                    imsx_CodeMajorType.failure);
            }
            else if (ReplaceResult(result))
            {
                response = CreateSuccessResponse(requestHeader.imsx_messageIdentifier,
                    $"Score for {replaceRequest.resultRecord.sourcedGUID.sourcedId} is now {replaceRequest.resultRecord.result.resultScore.textString}");
            }
            else
            {
                response = CreateCustomResponse(requestHeader.imsx_messageIdentifier,
                    $"Score for {replaceRequest.resultRecord.sourcedGUID.sourcedId} not replaced",
                    imsx_CodeMajorType.failure);
            }
            response.imsx_POXBody.Item = new replaceResultResponse();
            return response;
        }
        private imsx_POXEnvelopeType HandleDeleteResultRequest(imsx_RequestHeaderInfoType requestHeader, imsx_POXBodyType requestBody)
        {
            imsx_POXEnvelopeType response;
            var deleteRequest = requestBody.Item as deleteResultRequest ?? new deleteResultRequest();
            var deleteResponse = new deleteResultResponse();

            var result = GetResult(deleteRequest.resultRecord);
            if (DeleteResult(result.SourcedId))
            {
                response = CreateSuccessResponse(requestHeader.imsx_messageIdentifier,
                    $"Score for {result.SourcedId} is deleted");
            }
            else
            {
                response = CreateCustomResponse(requestHeader.imsx_messageIdentifier,
                    $"Score for {result.SourcedId} not deleted", imsx_CodeMajorType.failure);
            }
            response.imsx_POXBody.Item = deleteResponse;
            return response;
        }