Other Improved Ways To Export Data To Excel

 /// <summary>
        /// Exports to excel. 
        /// http://www.codeproject.com/Articles/9380/Export-a-DataSet-to-Microsoft-Excel-without-the-us
        /// http://bytes.com/topic/c-sharp/answers/497730-streamwriter-export-excel
        /// </summary>
        /// <param name="source">The source.</param>
        /// <param name="fileName">Name of the file.</param>
        /// <exception cref="System.Exception"></exception>
        public void ExportToExcel(DataSet source, string fileName)
        {

            //get response, set content type.
            HttpResponse response = HttpContext.Current.Response;
            response.ContentType = "application/vnd.ms-excel";
            response.AddHeader("Content-Disposition", "attachment;filename=\"" +
            fileName + "\"");
            response.Clear();
            System.IO.StreamWriter excelDoc;
            excelDoc = new System.IO.StreamWriter(response.OutputStream);


            /// excelDoc = new System.IO.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=\"0.0000\"/>\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=\"mm/dd/yyyy;@\"/>\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="0.0000"/>
           </Style>
           <Style ss:ID="Integer">
             <NumberFormat ss:Format="0"/>
           </Style>
           <Style ss:ID="DateLiteral">
             <NumberFormat ss:Format="mm/dd/yyyy;@"/>
           </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++)
                {
                    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);


            //flush and finish response
            excelDoc.Flush();
            excelDoc.Close();
            response.End();
        }

And to call it:


 /// <summary>
        /// Handles the Click event of the lbtnExportToExcel control.
        /// </summary>
        /// <param name="sender">The source of the event.</param>
        /// <param name="e">The <see cref="EventArgs"/> instance containing the event data.</param>
        protected void lbtnExportToExcel_Click(object sender, EventArgs e)
        {
            CommunicationsFilter filter = new CommunicationsFilter();

            filter = FilterControl.GetSearchFilter();
            int totalRowCount;
            List<SubscriberData> subData = CommDataManager.GetSubscribers(filter, 0, out totalRowCount);


            DataSet ds = new DataSet(); ds.Tables.Add(ConvertSubscriberDataToDataView(subData).ToTable());
            //ExportToExcel(ds, "MobileAlertsExport.xls");           

           

           
        }




  /// <summary>
        /// Converts the subscriber data to data view.
        /// </summary>
        /// <param name="subcriberData">The subcriber data.</param>
        /// <returns></returns>
        private DataView ConvertSubscriberDataToDataView(List<SubscriberData> subcriberData)
        {
            DataTable dt = new DataTable();

            // Define column headers
            dt.Columns.Add("First Name");
            dt.Columns.Add("Middle Initial");
            dt.Columns.Add("Last Name");
            dt.Columns.Add("Account Number");
            dt.Columns.Add("OPCO Abbrv Name");
            dt.Columns.Add("OPCO Full Name");
            dt.Columns.Add("Email");

            foreach (SubscriberData subscriber in subcriberData)
            {
                DataRow dr = dt.NewRow();

                dr["First Name"] = subscriber.FirstName;
                dr["Middle Initial"] = subscriber.MiddleInitial;
                dr["Last Name"] = subscriber.LastName;
                dr["Account Number"] = subscriber.SubscriberAccount.AccountNumberCheckDigit;
                dr["OPCO Abbrv Name"] = subscriber.OpCo.AbbreviatedName;
                dr["OPCO Full Name"] = subscriber.OpCo.FullName;
                dr["Email"] = subscriber.Email;

                dt.Rows.Add(dr);
            }

            //Load the datatable into a Dataview to accomodate easy sorting
            DataView dv = new DataView(dt);
            return dv;
        }

And for an even more native xlsx output check out http://www.mikesknowledgebase.com/pages/CSharp/ExportToExcel.htm# which uses DocumentFormat.OpenXML.dll

Export DataSet or DataTable to Excel

Function to get the results in datatable

private DataTable GetData(SqlCommand cmd)
{
    DataTable dt = new DataTable();
    String strConnString = System.Configuration.ConfigurationManager.
         ConnectionStrings["conString"].ConnectionString;
    SqlConnection con = new SqlConnection(strConnString);
    SqlDataAdapter sda = new SqlDataAdapter();
    cmd.CommandType = CommandType.Text;
    cmd.Connection = con;
    try
    {
        con.Open();
        sda.SelectCommand = cmd;
        sda.Fill(dt);
        return dt;
    }
    catch (Exception ex)
    {
        throw ex;
    }
    finally
    {
        con.Close();
        sda.Dispose();
        con.Dispose();
    }
}

Export to Excel

protected void ExportToExcel(object sender, EventArgs e)
{
    //Get the data from database into datatable
    string strQuery = "select CustomerID, ContactName, City, PostalCode" +
        " from customers";
    SqlCommand cmd = new SqlCommand(strQuery);
    DataTable dt = GetData(cmd);
 
    //Create a dummy GridView
    GridView GridView1 = new GridView();
    GridView1.AllowPaging = false;
    GridView1.DataSource = dt;
    GridView1.DataBind();
 
    Response.Clear();
    Response.Buffer = true;
    Response.AddHeader("content-disposition",
     "attachment;filename=DataTable.xls");
    Response.Charset = "";
    Response.ContentType = "application/vnd.ms-excel";
    StringWriter sw = new StringWriter();
    HtmlTextWriter hw = new HtmlTextWriter(sw);
 
    for (int i = 0; i < GridView1.Rows.Count; i++)
    {
        //Apply text style to each Row
        GridView1.Rows[i].Attributes.Add("class", "textmode");
    }
    GridView1.RenderControl(hw);
 
    //style to format numbers to string
    string style = @"<style> .textmode { mso-number-format:\@; } </style>";
    Response.Write(style);
    Response.Output.Write(sw.ToString());
    Response.Flush();
    Response.End();
}

Source from ASP Snippets