winform C# Export DataSet to Excel

 #region exportToExcel
        /// <summary>
        /// Export DataSet to Excel file
        /// </summary>
        /// <param name="source"></param>
        /// <param name="fileName"></param>
        public static void ExportToExcel(DataSet source, string fileName)
        {
            var excelDoc = new StreamWriter(fileName);
            const string startExcelXML = "<xml version>/r/n<Workbook " +
                  "xmlns=/"urn:schemas-microsoft-com:office:spreadsheet/"/r/n" +
                  " xmlns:o=/"urn:schemas-microsoft-com:office:office/"/r/n " +
                  "xmlns:x=/"urn:schemas-    microsoft-com:office:" +
                  "excel/"/r/n xmlns:ss=/"urn:schemas-microsoft-com:" +
                  "office:spreadsheet/">/r/n <Styles>/r/n " +
                  "<Style ss:ID=/"Default/" ss:Name=/"Normal/">/r/n " +
                  "<Alignment ss:Vertical=/"Bottom/"/>/r/n <Borders/>" +
                  "/r/n <Font/>/r/n <Interior/>/r/n <NumberFormat/>" +
                  "/r/n <Protection/>/r/n </Style>/r/n " +
                  "<Style ss:ID=/"BoldColumn/">/r/n <Font " +
                  "x:Family=/"Swiss/" ss:Bold=/"1/"/>/r/n </Style>/r/n " +
                  "<Style     ss:ID=/"StringLiteral/">/r/n <NumberFormat" +
                  " ss:Format=/"@/"/>/r/n </Style>/r/n <Style " +
                  "ss:ID=/"Decimal/">/r/n <NumberFormat " +
                  "ss:Format=/"#,##0.###/"/>/r/n </Style>/r/n " +
                  "<Style ss:ID=/"Integer/">/r/n <NumberFormat " +
                  "ss:Format=/"0/"/>/r/n </Style>/r/n <Style " +
                  "ss:ID=/"DateLiteral/">/r/n <NumberFormat " +
                  "ss:Format=/"yyyy-mm-dd;@/"/>/r/n </Style>/r/n " +
                  "</Styles>/r/n ";
            const string endExcelXML = "</Workbook>";

            int rowCount = 0;
            int sheetCount = 1;
            /*
           <xml version>
           <Workbook xmlns="urn:schemas-microsoft-com:office:spreadsheet"
           xmlns:o="urn:schemas-microsoft-com:office:office"
           xmlns:x="urn:schemas-microsoft-com:office:excel"
           xmlns:ss="urn:schemas-microsoft-com:office:spreadsheet">
           <Styles>
           <Style ss:ID="Default" ss:Name="Normal">
             <Alignment ss:Vertical="Bottom"/>
             <Borders/>
             <Font/>
             <Interior/>
             <NumberFormat/>
             <Protection/>
           </Style>
           <Style ss:ID="BoldColumn">
             <Font x:Family="Swiss" ss:Bold="1"/>
           </Style>
           <Style ss:ID="StringLiteral">
             <NumberFormat ss:Format="@"/>
           </Style>
           <Style ss:ID="Decimal">
             <NumberFormat ss:Format="#,##0.###"/>
           </Style>
           <Style ss:ID="Integer">
             <NumberFormat ss:Format="0"/>
           </Style>
           <Style ss:ID="DateLiteral">
             <NumberFormat ss:Format="yyyy-mm-dd;@"/>
           </Style>
           </Styles>
           <Worksheet ss:Name="Sheet1">
           </Worksheet>
           </Workbook>
           */
            excelDoc.Write(startExcelXML);
            excelDoc.Write("<Worksheet ss:Name=/"Sheet" + sheetCount + "/">");
            excelDoc.Write("<Table>");
            excelDoc.Write("<Row>");
            for (int x = 0; x < source.Tables[0].Columns.Count; x++)
            {
                excelDoc.Write("<Cell ss:StyleID=/"BoldColumn/"><Data ss:Type=/"String/">");
                excelDoc.Write(source.Tables[0].Columns[x].ColumnName);
                excelDoc.Write("</Data></Cell>");
            }
            excelDoc.Write("</Row>");
            foreach (DataRow x in source.Tables[0].Rows)
            {
                rowCount++;
                //if the number of rows is > 64000 create a new page to continue output

                if (rowCount == 64000)
                {
                    rowCount = 0;
                    sheetCount++;
                    excelDoc.Write("</Table>");
                    excelDoc.Write(" </Worksheet>");
                    excelDoc.Write("<Worksheet ss:Name=/"Sheet" + sheetCount + "/">");
                    excelDoc.Write("<Table>");
                }
                excelDoc.Write("<Row>"); //ID=" + rowCount + "

                for (int y = 0; y < source.Tables[0].Columns.Count; y++)
                {
                    Type rowType = x[y].GetType();
                    switch (rowType.ToString())
                    {
                        case "System.String":
                            string XMLstring = x[y].ToString();
                            XMLstring = XMLstring.Trim();
                            XMLstring = XMLstring.Replace("&", "&");
                            XMLstring = XMLstring.Replace(">", ">");
                            XMLstring = XMLstring.Replace("<", "<");
                            excelDoc.Write("<Cell ss:StyleID=/"StringLiteral/">" +
                                           "<Data ss:Type=/"String/">");
                            excelDoc.Write(XMLstring);
                            excelDoc.Write("</Data></Cell>");
                            break;
                        case "System.DateTime":
                            //Excel has a specific Date Format of YYYY-MM-DD followed by 

                            //the letter 'T' then hh:mm:sss.lll Example 2005-01-31T24:01:21.000

                            //The Following Code puts the date stored in XMLDate

                            //to the format above

                            var XMLDate = (DateTime)x[y];

                            string XMLDatetoString = XMLDate.Year +
                                                     "-" +
                                                     (XMLDate.Month < 10
                                                          ? "0" +
                                                            XMLDate.Month
                                                          : XMLDate.Month.ToString()) +
                                                     "-" +
                                                     (XMLDate.Day < 10
                                                          ? "0" +
                                                            XMLDate.Day
                                                          : XMLDate.Day.ToString()) +
                                                     "T" +
                                                     (XMLDate.Hour < 10
                                                          ? "0" +
                                                            XMLDate.Hour
                                                          : XMLDate.Hour.ToString()) +
                                                     ":" +
                                                     (XMLDate.Minute < 10
                                                          ? "0" +
                                                            XMLDate.Minute
                                                          : XMLDate.Minute.ToString()) +
                                                     ":" +
                                                     (XMLDate.Second < 10
                                                          ? "0" +
                                                            XMLDate.Second
                                                          : XMLDate.Second.ToString()) +
                                                     ".000";
                            excelDoc.Write("<Cell ss:StyleID=/"DateLiteral/">" +
                                         "<Data ss:Type=/"DateTime/">");
                            excelDoc.Write(XMLDatetoString);
                            excelDoc.Write("</Data></Cell>");
                            break;
                        case "System.Boolean":
                            excelDoc.Write("<Cell ss:StyleID=/"StringLiteral/">" +
                                        "<Data ss:Type=/"String/">");
                            excelDoc.Write(x[y].ToString());
                            excelDoc.Write("</Data></Cell>");
                            break;
                        case "System.Int16":
                        case "System.Int32":
                        case "System.Int64":
                        case "System.Byte":
                            excelDoc.Write("<Cell ss:StyleID=/"Integer/">" +
                                    "<Data ss:Type=/"Number/">");
                            excelDoc.Write(x[y].ToString());
                            excelDoc.Write("</Data></Cell>");
                            break;
                        case "System.Decimal":
                        case "System.Double":
                            excelDoc.Write("<Cell ss:StyleID=/"Decimal/">" +
                                  "<Data ss:Type=/"Number/">");
                            excelDoc.Write(x[y].ToString());
                            excelDoc.Write("</Data></Cell>");
                            break;
                        case "System.DBNull":
                            excelDoc.Write("<Cell ss:StyleID=/"StringLiteral/">" +
                                  "<Data ss:Type=/"String/">");
                            excelDoc.Write("");
                            excelDoc.Write("</Data></Cell>");
                            break;
                        default:
                            throw (new Exception(rowType.ToString() + " not handled."));
                    }
                }
                excelDoc.Write("</Row>");
            }
            excelDoc.Write("</Table>");
            excelDoc.Write(" </Worksheet>");
            excelDoc.Write(endExcelXML);
            excelDoc.Close();
        }
        #endregion exportToExcel