ACCESS Database - Check if User is in DB if not then alert

Question

Please see my script and help. IT HAS TO BE ACCESS DB and NOT SQL.

private void tableqry() {

 try {
  connection.Open();
  OleDbCommand command = new OleDbCommand();
  command.Connection = connection;
  string query = "select *," +
   "(Course1 + Course2 + Course3 + Course4+ Course5 + Course6 + Course7 + Course8 + Course9 + Course10) / 10 AS AvgMark " +
   "from Students WHERE Firstname LIKE '" + tbsearchid.Text + "' OR " + "ID1 like '" + tbsearchid.Text + "'";
  command.CommandText = query;
  OleDbDataReader reader = command.ExecuteReader();
  while (reader.Read()) {

   tbFname.Text = reader["Firstname"].ToString();
   tbLname.Text = reader["Lastname"].ToString();

   string course1Text = reader["Course1"].ToString(), course2Text = reader["Course2"].ToString(),
    course3Text = reader["Course3"].ToString(), course4Text = reader["Course4"].ToString(),
    course5Text = reader["Course5"].ToString(), course6Text = reader["Course6"].ToString(),
    course7Text = reader["Course7"].ToString(), course8Text = reader["Course8"].ToString(),
    course9Text = reader["Course9"].ToString(), course10Text = reader["Course10"].ToString();

   tbmulti.Text = "Course1: " + course1Text + Environment.NewLine + "Course2: " + course2Text +
    Environment.NewLine + "Course3: " + course3Text + Environment.NewLine + "Course4: " + course4Text +
    Environment.NewLine + "Course5: " + course5Text + Environment.NewLine + "Course6: " + course6Text +
    Environment.NewLine + "Course7: " + course7Text + Environment.NewLine + "Course8: " + course8Text +
    Environment.NewLine + "Course9: " + course9Text + Environment.NewLine + "Course10: " + course10Text;

   int[] marks = new int[10] {
    Convert.ToInt32(reader["Course1"]), Convert.ToInt32(reader["Course2"]),
     Convert.ToInt32(reader["Course3"]), Convert.ToInt32(reader["Course4"]),
     Convert.ToInt32(reader["Course5"]), Convert.ToInt32(reader["Course6"]),
     Convert.ToInt32(reader["Course7"]), Convert.ToInt32(reader["Course8"]),
     Convert.ToInt32(reader["Course9"]), Convert.ToInt32(reader["Course10"])
   };

   int avgmarks = sumAverageElements(marks, marks.Length);

   if (avgmarks <= 40) {
    tbrate.Text = "Fail";
   } else if (avgmarks <= 59) {
    tbrate.Text = "Pass";
   } else if (avgmarks <= 79) {
    tbrate.Text = "Good";
   } else if (avgmarks <= 100) {
    tbrate.Text = "Excellent";
   }

   tbhighmark.Text = marks.Max().ToString();
   tblowmark.Text = marks.Min().ToString();
   tbCourseAvg.Text = avgmarks.ToString();
  }
  connection.Close();
 } catch (Exception ex) {
  MessageBox.Show("Error    " + ex);

 }
}