export dataset in multiple excelsheet in asp.net

<asp:TextBox ID="txtname" runat="server"></asp:TextBox> 

<asp:Button ID="Export" runat="server" Text="Export" OnClick="Export_Click" />

public void DataSetToExcelSheet(DataSet source, string fileName)

 {

string strPath = Server.MapPath("ExcelFile"); //folder get pathSystem.IO.StreamWriter excelDoc = new System.IO.StreamWriter(strPath+"/" + fileName);

const string startExcelXML = "<xml version>rn<Workbook "

+"xmlns="urn:schemas-microsoft-com:office:spreadsheet"rn"

+ " xmlns:o="urn:schemas-microsoft-com:office:office"rn "

+ "xmlns:x="urn:schemas- microsoft-com:office:"

+ "excel"rn xmlns:ss="urn:schemas-microsoft-com:"

+ "office:spreadsheet">rn <Styles>rn "

+ "<Style ss:ID="Default" ss:Name="Normal">rn "

+ "<Alignment ss:Vertical="Bottom"/>rn <Borders/>"

+ "rn <Font/>rn <Interior/>rn <NumberFormat/>"

+ "rn <Protection/>rn </Style>rn "

+ "<Style ss:ID="BoldColumn">rn <Font "

+ "x:Family="Swiss" ss:Bold="1"/>rn </Style>rn "

+ "<Style ss:ID="StringLiteral">rn <NumberFormat"

+ " ss:Format="@"/>rn </Style>rn <Style "

+ "ss:ID="Decimal">rn <NumberFormat "

+ "ss:Format="0.0000"/>rn </Style>rn "

+ "<Style ss:ID="Integer">rn <NumberFormat "

+ "ss:Format="0"/>rn </Style>rn <Style "

+ "ss:ID="DateLiteral">rn <NumberFormat "

+ "ss:Format="mm/dd/yyyy;@"/>rn </Style>rn "

+ "</Styles>rn ";

const string endExcelXML = "</Workbook>";

int rowCount = 0;

int sheetCount = 1; //Sheet

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++)

{ 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.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

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.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();

}

protected void Export_Click(object sender, EventArgs e)

{

SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["connect"].ConnectionString);

SqlDataAdapter sda = new SqlDataAdapter("select top 100000 regid,companyname from registration order by regid", con);

DataSet ds = new DataSet();

sda.Fill(ds);

DataSetToExcelSheet(ds, txtname.Text+".xls");

}