asp.net gridview

Question

i have table student with 5 columns that is student_id,student_name,student_class,student_gender,student_position, i only want show 3 columns that is student_name,student_class ,student_position i use this query

select  student_name,student_class ,student_position from student,the issue is whenever i come to load my gridview i got the rest two columns what will i do to hide the 

have tried this but not working

gdvstudent.Columns[1].Visible=false;

but not working ,anybody with idea help please using asp.net c#