How to filter row from DataTable ?

DataRow[] drMarks  = dvstudentMarks.Table.Select("displayGroupname='" + GetDisplayGroupID(dvSubjectName.Table.Rows[intsubjectName]["subjectID"].ToString(), FA1.Trim()) + "'and termID='" + FirstTermId + "'");
if (drMarks.Length > 0)
{
// Each colum
    foreach (DataRow rowObtainedWM in drMarks)
    {

       // str.Append("    <td colspan=2 class=xl71 style='border-left:none'>" + rowObtainedWM["Grade"].ToString() + "</td>    ");

    }
}
else
    str.Append("<td colspan=2 class=xl71 style='border-left:none'>&nbsp;</td>    ");