ASP.NET

 Dim spreadsheet As DocumentFormat.OpenXml.Packaging.SpreadsheetDocument
        Dim worksheet As DocumentFormat.OpenXml.Spreadsheet.Worksheet
        Dim styleXml As String

        spreadsheet = Excel.CreateWorkbook(workbookName)
        If (spreadsheet Is Nothing) Then
            Return
        End If
        Excel.AddWorksheet(spreadsheet, "Test")
        worksheet = spreadsheet.WorkbookPart.WorksheetParts.First().Worksheet
?????
worksheet.Save()

ReportViewer rptvw1 = new ReportViewer();
       rptvw1.ProcessingMode = ProcessingMode.Local;
       rptvw1.LocalReport.ReportPath = p.Server.MapPath("~/GridReport.rdlc");
       BL_Insurance.PrintDetail print = new BL_Insurance.PrintDetail();
       DataTable ds = print.Print(Convert.ToInt32(p.Session["transactionid"]), Convert.ToString(p.Session["typeofplan"]), Convert.ToInt32(p.Session["UserID"]));
       ReportDataSource datasource = new ReportDataSource("DataSet1", ds);
       rptvw1.LocalReport.DataSources.Clear();
       rptvw1.LocalReport.DataSources.Add(datasource);
       ReportParameter[] param = new ReportParameter[4];
       param[0] = new ReportParameter("Company", Convert.ToString(p.Session["insurancecompany"]));
       param[1] = new ReportParameter("Policy", Convert.ToString(p.Session["policyname"]));
       if (ds.Columns.Contains("Adult"))
       {
           param[2] = new ReportParameter("Adult", "True");
           param[3] = new ReportParameter("Child", "True");
       }

       else
       {
           param[2] = new ReportParameter("Adult", "False");
           param[3] = new ReportParameter("Child", "False");
       }
       rptvw1.LocalReport.SetParameters(param);
       rptvw1.LocalReport.Refresh();
       Warning[] warnings = null;
       string[] streamIds = null;
       string mimeType = string.Empty;
       string encoding = string.Empty;
       string extension = string.Empty;
       filetype = "PDF";
       fname = DateTime.Now.ToString("yyyyMMddHHmmssfff");
       byte[] bytes = rptvw1.LocalReport.Render(filetype, null, out mimeType, out encoding, out extension, out streamIds, out warnings);

DataTable Dt = new DataTable();
Dt.Columns.Add("File", typeof(string));
Dt.Columns.Add("Size", typeof(string));
Dt.Columns.Add("Dir", typeof(string));
foreach (string filename in Directory.GetFiles(@"C:\files"))
{
    FileInfo fileinfo = new FileInfo(filename);
    Dt.Rows.Add(fileinfo.Name, fileinfo.Length +"KB", fileinfo.FullName);


}
GridView1.DataSource = Dt;
GridView1.DataBind();