วิธีแสดงผล query mysql แสดงเครื่องหมาย " กรณีข้อมูลซ้ำกัน

sql = "select subject_group, subject_id, subject_name from subject group by subject_group order by subject_group asc"

string subject_group_tmp = "";
 while (reader.Read())
 {
             $subject_group = reader.GetString(1); 
             $subject_id = reader.GetInt32(0); 
             $subject_name = reader.GetString(2);

if(subject_group_tmp = subject_group)
        //Console.WriteLine("subject_group = {0}, subject_id = {1}, subject_name = {2}", subject_group, subject_id, subject_name);
        //echo "<tr><td>$subject_group</td><td>$subject_id</td><td>$subject_name</td></tr>";
else
        //Console.WriteLine("subject_group = "", subject_id = {1}, subject_name = {2}", subject_group, subject_id, subject_name);
       ///echo "<tr><td>$subject_group</td><td>$subject_id</td><td>$subject_name</td></tr>";
end if

subject_group_tmp = subject_group;

 }