Export Excel

public void CreateExcel(DataTable source, string fileName, HttpContext context)
    {

        StringBuilder excelDoc = new StringBuilder();

        const string startExcelXML = @"<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=\"0.0000\"/>  </Style>  " +
              "<Style ss:ID=\"Integer\">  <NumberFormat " +
              "ss:Format=\"0\"/>  </Style>  <Style " +
              "ss:ID=\"DateLiteral\">  <NumberFormat " +
              "ss:Format=\"mm/dd/yyyy;@\"/>  </Style>  " +
              "</Styles>  ";
        const string endExcelXML = "</Workbook>";

        int rowCount = 0;
        int sheetCount = 1;

        excelDoc.Append(startExcelXML);
        excelDoc.Append("<Worksheet ss:Name=\"Sheet" + sheetCount + "\">");
        excelDoc.Append("<Table>");
        excelDoc.Append("<Row>");
        for (int x = 0; x < source.Columns.Count; x++)
        {
            excelDoc.Append("<Cell ss:StyleID=\"BoldColumn\"><Data ss:Type=\"String\">");
            excelDoc.Append(source.Columns[x].ColumnName);
            excelDoc.Append("</Data></Cell>");
        }
        excelDoc.Append("</Row>");
        foreach (DataRow x in source.Rows)
        {
            rowCount++;
            //if the number of rows is > 64000 create a new page to continue output
            if (rowCount == 64000)
            {
                rowCount = 0;
                sheetCount++;
                excelDoc.Append("</Table>");
                excelDoc.Append(" </Worksheet>");
                excelDoc.Append("<Worksheet ss:Name=\"Sheet" + sheetCount + "\">");
                excelDoc.Append("<Table>");
            }
            excelDoc.Append("<Row>"); //ID=" + rowCount + "
            for (int y = 0; y < source.Columns.Count; y++)
            {
                System.Type rowType;
                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.Append("<Cell ss:StyleID=\"StringLiteral\">" +
                                       "<Data ss:Type=\"String\">");
                        excelDoc.Append(XMLstring);
                        excelDoc.Append("</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
                        DateTime XMLDate = (DateTime)x[y];
                        string XMLDatetoString = ""; //Excel Converted Date
                        XMLDatetoString = XMLDate.Year.ToString() +
                             "-" +
                             (XMLDate.Month < 10 ? "0" +
                             XMLDate.Month.ToString() : XMLDate.Month.ToString()) +
                             "-" +
                             (XMLDate.Day < 10 ? "0" +
                             XMLDate.Day.ToString() : XMLDate.Day.ToString()) +
                             "T" +
                             (XMLDate.Hour < 10 ? "0" +
                             XMLDate.Hour.ToString() : XMLDate.Hour.ToString()) +
                             ":" +
                             (XMLDate.Minute < 10 ? "0" +
                             XMLDate.Minute.ToString() : XMLDate.Minute.ToString()) +
                             ":" +
                             (XMLDate.Second < 10 ? "0" +
                             XMLDate.Second.ToString() : XMLDate.Second.ToString()) +
                             ".000";
                        excelDoc.Append("<Cell ss:StyleID=\"DateLiteral\">" +
                                     "<Data ss:Type=\"DateTime\">");
                        excelDoc.Append(XMLDatetoString);
                        excelDoc.Append("</Data></Cell>");
                        break;
                    case "System.Boolean":
                        excelDoc.Append("<Cell ss:StyleID=\"StringLiteral\">" +
                                    "<Data ss:Type=\"String\">");
                        excelDoc.Append(x[y].ToString());
                        excelDoc.Append("</Data></Cell>");
                        break;
                    case "System.Int16":
                    case "System.Int32":
                    case "System.Int64":
                    case "System.Byte":
                        excelDoc.Append("<Cell ss:StyleID=\"Integer\">" +
                                "<Data ss:Type=\"Number\">");
                        excelDoc.Append(x[y].ToString());
                        excelDoc.Append("</Data></Cell>");
                        break;
                    case "System.Decimal":
                    case "System.Double":
                        excelDoc.Append("<Cell ss:StyleID=\"Decimal\">" +
                              "<Data ss:Type=\"Number\">");
                        excelDoc.Append(x[y].ToString());
                        excelDoc.Append("</Data></Cell>");
                        break;
                    case "System.DBNull":
                        excelDoc.Append("<Cell ss:StyleID=\"StringLiteral\">" +
                              "<Data ss:Type=\"String\">");
                        excelDoc.Append("");
                        excelDoc.Append("</Data></Cell>");
                        break;
                    default:
                        throw (new Exception(rowType.ToString() + " not handled."));
                }
            }
            excelDoc.Append("</Row>");
        }
        excelDoc.Append("</Table>");
        excelDoc.Append(" </Worksheet>");
        excelDoc.Append(endExcelXML);


        byte[] strdata = System.Text.Encoding.Default.GetBytes(excelDoc.ToString());

        context.Response.ContentType = "application/octet-stream";
        context.Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));
        context.Response.BinaryWrite(strdata);
        context.Response.Flush();
        context.Response.End();
    }