Generate XML using StringBuilder in ASP.Net

 is this right to generate xml like this

        string generateXMLDificiencyResaon(List<DiscrepancyCaseModel> model)
        {
            System.Text.StringBuilder sb = new System.Text.StringBuilder();
            if (model != null)
            {
                sb.Append("<ArrayOfDiscrepancyCaseModel>");
                foreach (var data in model)
                {
                    sb.Append("<DiscrepancyCaseModel>");
                    sb.Append("<caseId>" + data.caseId + "</caseId>");
                    sb.Append("<CaseReasonId>" + string.Join(",", data.CaseReasonId) + "</CaseReasonId>");
                    sb.Append("<OtherReason>" + data.OtherReason + "</OtherReason>");
                    sb.Append("<checkboxFlag>" + data.checkboxFlag + "</checkboxFlag>");
                    sb.Append("</DiscrepancyCaseModel>");

                }
                sb.Append("</ArrayOfDiscrepancyCaseModel>");
            }

            return sb.ToString();
        }