XuGang

//ExcelHelper.cs

public class ExcelHelper
{
    //Row limits older Excel version per sheet
        const int rowLimit = 65000;

        private static string getWorkbookTemplate()
        {
            var sb = new StringBuilder();
            sb.Append("<xml version>\r\n<Workbook
        xmlns=\"urn:schemas-microsoft-com:office:spreadsheet\"\r\n");
            sb.Append(" 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");
            sb.Append(" <Styles>\r\n
        <Style ss:ID=\"Default\" ss:Name=\"Normal\">\r\n
        <Alignment ss:Vertical=\"Bottom\"/>\r\n <Borders/>");
            sb.Append("\r\n <Font/>\r\n <Interior/>\r\n <NumberFormat/>\r\n
        <Protection/>\r\n </Style>\r\n
        <Style ss:ID=\"BoldColumn\">\r\n <Font ");
            sb.Append("x:Family=\"Swiss\" ss:Bold=\"1\"/>\r\n </Style>\r\n
        <Style ss:ID=\"s62\">\r\n <NumberFormat");
            sb.Append(" ss:Format=\"@\"/>\r\n </Style>\r\n
        <Style ss:ID=\"Decimal\">\r\n
        <NumberFormat ss:Format=\"0.0000\"/>\r\n </Style>\r\n ");
            sb.Append("<Style ss:ID=\"Integer\">\r\n
        <NumberFormat ss:Format=\"0\"/>\r\n </Style>\r\n
        <Style ss:ID=\"DateLiteral\">\r\n <NumberFormat ");
            sb.Append("ss:Format=\"mm/dd/yyyy;@\"/>\r\n </Style>\r\n
        <Style ss:ID=\"s28\">\r\n");
            sb.Append("<Alignment ss:Horizontal=\"Left\" ss:Vertical=\"Top\"
        ss:ReadingOrder=\"LeftToRight\" ss:WrapText=\"1\"/>\r\n");
            sb.Append("<Font x:CharSet=\"1\" ss:Size=\"9\"
        ss:Color=\"#808080\" ss:Underline=\"Single\"/>\r\n");
            sb.Append("<Interior ss:Color=\"#FFFFFF\" ss:Pattern=\"Solid\"/>

        </Style>\r\n</Styles>\r\n {0}</Workbook>");
            return sb.ToString();
        }

        private static string replaceXmlChar(string input)
        {
            input = input.Replace("&", "&");
            input = input.Replace("<", "<");
            input = input.Replace(">", ">");
            input = input.Replace("\"", """);
            input = input.Replace("'", "'");
            return input;
        }

        private static string getWorksheets(DataSet source)
        {
            var sw = new StringWriter();
            if (source == null || source.Tables.Count == 0)
            {
                sw.Write("<Worksheet ss:Name=\"Sheet1\"><Table><Row>

        <Cell  ss:StyleID=\"s62\"><Data ss:Type=\"String\"></Data>
        </Cell></Row></Table></Worksheet>");
                return sw.ToString();
            }
            foreach (DataTable dt in source.Tables)
            {
                if (dt.Rows.Count == 0)
                    sw.Write("<Worksheet ss:Name=\"" + replaceXmlChar(dt.TableName) +
            "\"><Table><Row><Cell  ss:StyleID=\"s62\">

            <Data ss:Type=\"String\"></Data></Cell></Row>
            </Table></Worksheet>");
                else
                {
                    //write each row data
                    var sheetCount = 0;
                    for (int i = 0; i < dt.Rows.Count; i++)
                    {
                        if ((i % rowLimit) == 0)
                        {
                            //add close tags for previous sheet of the same data table
                            if ((i / rowLimit) > sheetCount)
                            {
                                sw.Write("</Table></Worksheet>");
                                sheetCount = (i / rowLimit);
                            }
                            sw.Write("<Worksheet ss:Name=\"" +
                replaceXmlChar(dt.TableName) +
                                     (((i / rowLimit) == 0) ? "" :
                Convert.ToString(i / rowLimit)) + "\"><Table>");
                            //write column name row
                            sw.Write("<Row>");
                            foreach (DataColumn dc in dt.Columns)
                                sw.Write(
                                    string.Format(
                                        "<Cell ss:StyleID=\"BoldColumn\">

                <Data ss:Type=\"String\">{0}</Data></Cell>",
                                        replaceXmlChar(dc.ColumnName)));
                            sw.Write("</Row>\r\n");
                        }
                        sw.Write("<Row>\r\n");
                        foreach (DataColumn dc in dt.Columns)
                            sw.Write(
                                string.Format(
                                    "<Cell ss:StyleID=\"s62\"><Data ss:Type=\"String\">

                    {0}</Data></Cell>",
                                            replaceXmlChar
                    (dt.Rows[i][dc.ColumnName].ToString())));
                        sw.Write("</Row>\r\n");
                    }
                    sw.Write("</Table></Worksheet>");
                }
            }

            return sw.ToString();
        }
        public static string GetExcelXml(DataTable dtInput, string filename)
        {
            var excelTemplate = getWorkbookTemplate();
            var ds = new DataSet();
            ds.Tables.Add(dtInput.Copy());
            var worksheets = getWorksheets(ds);
            var excelXml = string.Format(excelTemplate, worksheets);
            return excelXml;
        }

        public static string GetExcelXml(DataSet dsInput, string filename)
        {
            var excelTemplate = getWorkbookTemplate();
            var worksheets = getWorksheets(dsInput);
            var excelXml = string.Format(excelTemplate, worksheets);
            return excelXml;
        }

        public static void ToExcel
        (DataSet dsInput, string filename, HttpResponse response)
        {
            var excelXml = GetExcelXml(dsInput, filename);
            response.Clear();
            response.AppendHeader("Content-Type", "application/vnd.ms-excel");
            response.AppendHeader
        ("Content-disposition", "attachment; filename=" + filename);
            response.Write(excelXml);
            response.Flush();
            response.End();
        }

        public static void ToExcel
        (DataTable dtInput, string filename, HttpResponse response)
        {
            var ds = new DataSet();
            ds.Tables.Add(dtInput.Copy());
            ToExcel(ds, filename, response);
        }
    }