excel export using EPPlus

Have a look at ExeclPackagePlus http://epplus.codeplex.com

It's great for these kinds of scenarios.

 private void DumpExcel(DataTable tbl)
    {
        try{
         //   OfficeOpenXml.ExcelPackage
        using (ExcelPackage pck = new ExcelPackage())
        {
            //Create the worksheet
            ExcelWorksheet ws = pck.Workbook.Worksheets.Add("Mailing List");

            //Load the datatable into the sheet, starting from cell A1. Print the column names on row 1
            ws.Cells["A2"].LoadFromDataTable(tbl, false);

            //Header Titles
            ws.Cells["A1"].Value = "Employee Name";
            ws.Cells["B1"].Value = "Email Address";
            ws.Cells["C1"].Value = "Phone";
            ws.Cells["D1"].Value = "Business Unit";
            ws.Cells["E1"].Value = "Site";

            ws.Cells["A1"].AutoFitColumns();

            //Format the header for column 1-3
            using (ExcelRange rng = ws.Cells["A1:E1"])            {
              
                rng.Style.Font.Bold = true;
                //Set Pattern for the background to Solid
                rng.Style.Fill.PatternType = ExcelFillStyle.Solid;
                //Set color to dark blue
                rng.Style.Fill.BackgroundColor.SetColor(System.Drawing.Color.FromArgb(79, 129, 189));
                rng.Style.Font.Color.SetColor(System.Drawing.Color.White);
            }


            //Write it back to the client          

            Response.Clear();
            Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
            Response.AddHeader("content-disposition", "attachment;  filename=MailingList.xlsx");
            Response.BinaryWrite(pck.GetAsByteArray());           
        }
        }
        catch (Exception ex) 
        {
    //log error
        }
           Response.End();
        }