Interop Excel: Before Saving the Excel file delete the old file in C# .Net

 My code as follows

i want to delete the old file and replace the new one.

 private void Preseaintake()
        {
            try
            {
                SqlCommand cmd = new SqlCommand();
                cmd.Connection = con;
                cmd.CommandText = "Presea_Intakerpts '" + dtfromdate.Text.Trim() + "', '" + dttodate.Text.Trim() + "'";
                SqlDataAdapter adp = new SqlDataAdapter(cmd);
                DataTable table = new DataTable();
                adp.Fill(table);

                Microsoft.Office.Interop.Excel.Application xlapp = new Microsoft.Office.Interop.Excel.Application();
                Microsoft.Office.Interop.Excel.Workbook xlWorkBook;
                Microsoft.Office.Interop.Excel.Worksheet xlsheet;
                object misvalue = System.Reflection.Missing.Value;
               
                xlWorkBook = (Microsoft.Office.Interop.Excel.Workbook)xlapp.Workbooks.Add(1);
                xlsheet = (Microsoft.Office.Interop.Excel.Worksheet)xlWorkBook.ActiveSheet;

                for (int i = 0; i < table.Columns.Count; i++)
                {
                    xlsheet.Cells[1, i + 1] = table.Columns[i].ColumnName;

                }
                for (int i = 0; i < table.Rows.Count; i++)
                {
                    for (int j = 0; j < table.Columns.Count; j++)
                    {
                        xlsheet.Cells[i + 2, j + 1] = table.Rows[i][j].ToString().Trim();
                    }
                }

                xlWorkBook.SaveAs(Application.StartupPath + "\\Preseaintake\\newtest.xls", misvalue, misvalue, misvalue, misvalue, misvalue, Microsoft.Office.Interop.Excel.XlSaveAsAccessMode.xlExclusive, misvalue, misvalue,
                         misvalue, misvalue, misvalue);
                xlWorkBook.Close(true, misvalue, misvalue);
                xlsheet = null;
                xlapp = null;
            }

            catch (Exception ex)
            {
                MessageBox.Show(ex.ToString(), "Error", MessageBoxButtons.OK);
                return;
            }

        }



 private void sendmail()
        {
            try
            {
                MailMessage mis = new MailMessage(); 
                SmtpClient smtpserver = new SmtpClient("smtp.gmail.com");
                smtpserver.Credentials = new NetworkCredential("reply@gmail.com", "hdfdf");
                smtpserver.Host = "smtp.gmail.com";
                smtpserver.Port = 587;
                smtpserver.EnableSsl = true;
                mis.From = new MailAddress("reply@gmail.com", "PreseaIntakeDetails");
                mis.IsBodyHtml = true;
                mis.To.Add("gdf@gmail.com");
                mis.Subject = "PreseaIntake Report";

                System.Net.Mail.Attachment attachment;
                 attachment = new System.Net.Mail.Attachment(Application.StartupPath +               "\\Preseaintake\\newtest.xls");
                mis.Attachments.Add(attachment);
                smtpserver.Send(mis);
                mis.DeliveryNotificationOptions = DeliveryNotificationOptions.OnFailure;
            }

            catch (Exception ex)
            {
                MessageBox.Show(ex.ToString(), "Error", MessageBoxButtons.OK);
                return;
            }
        }


i want to delete the old file and replace with new one.

for that how can i do?

in my above code what changes i have to made.

please help me.

regards,
narasiman P.