want to insert one field in gridview after i import that field

protected void Button2_Click(object sender, EventArgs e)
        {
            string srvFileLocation = "";
            string fileName = "", fileExtension = "";
            string connectionString = "";
            if (FileUpload1.HasFile)
            {
                fileName = Path.GetFileName(FileUpload1.PostedFile.FileName);
                fileExtension = Path.GetExtension(FileUpload1.PostedFile.FileName);
                string fileLocation = Server.MapPath("~/App_Data/" + fileName);
                FileUpload1.SaveAs(fileLocation);
                Label1.Text = "File Uploaded: " + FileUpload1.FileName;
                //Check whether file extension is xls or xslx

                if (fileExtension == ".xls")
                {
                    connectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + fileLocation + ";Extended Properties=\"Excel 8.0;HDR=Yes;IMEX=2\"";
                }
                else if (fileExtension == ".xlsx")
                {
                    connectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + fileLocation + ";Extended Properties=\"Excel 12.0;HDR=Yes;IMEX=2\"";
                }
                //  String cn = "Provider=Microsoft.Jet.OLEDB.4.0;" +"Data Source=C:\\Users\\Charu\\Documents;" +"Extended Properties=Excel 8.0;";
                //Create OleDB Connection and OleDb Command

                OleDbConnection con = new OleDbConnection(connectionString);
                OleDbCommand cmd = new OleDbCommand();
                cmd.CommandType = System.Data.CommandType.Text;
                cmd.Connection = con;
                OleDbDataAdapter dAdapter = new OleDbDataAdapter(cmd);
                DataTable dtExcelRecords = new DataTable();
                con.Open();
                DataTable dtExcelSheetName = con.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, null);
                string getExcelSheetName = dtExcelSheetName.Rows[0]["Table_Name"].ToString();
                cmd.CommandText = "SELECT * FROM [" + getExcelSheetName + "]";
                dAdapter.SelectCommand = cmd;
                dAdapter.Fill(dtExcelRecords);
                con.Close();
                GridView1.DataSource = dtExcelRecords;
                GridView1.DataBind();

            }
            else
            {
                Label1.Text = "No File Uploaded.";
            }

            if (FileUpload1.HasFile)
            {
                fileName = Path.GetFileName(FileUpload1.PostedFile.FileName);
                fileExtension = Path.GetExtension(FileUpload1.PostedFile.FileName);
                srvFileLocation = Server.MapPath("~/App_Data/" + fileName);
                FileUpload1.SaveAs(srvFileLocation);

            }
            string excelConnectionString = "";
            if (fileExtension == ".xls")
            {
                excelConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + srvFileLocation + ";Extended Properties=\"Excel 8.0;HDR=Yes;IMEX=2\"";
            }
            else if (fileExtension == ".xlsx")
            {
                excelConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + srvFileLocation + ";Extended Properties=\"Excel 12.0;HDR=Yes;IMEX=2\"";
            }
            //string excelConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + srvFileLocation + ";Extended Properties=\"Excel 8.0;HDR=Yes;IMEX=2\"";

            // Create Connection to Excel 
            using (OleDbConnection connection = new OleDbConnection(excelConnectionString))
            {
                OleDbCommand command = new OleDbCommand("Select * FROM [Sheet1$]", connection);
                connection.Open();
                // Create DbDataReader to Data Worksheet
                using (DbDataReader dr = command.ExecuteReader())
                {
                    // SQL Server Connection String
                    string sqlConnectionString = "Data Source=SNSWAMY\\SQLEXPRESS;Initial Catalog=payroll;Persist Security Info=True;User ID=avoc;Password=avoc123";

                    // Bulk Copy to SQL Server
                    using (SqlBulkCopy bulkCopy = new SqlBulkCopy(sqlConnectionString))
                    {
                        //bulkCopy.ColumnMappings.Add("process_datetime", "process_datetime");
                        bulkCopy.DestinationTableName = "leave_tran";
                        bulkCopy.WriteToServer(dr);
                    }
                }
            }
            }