How to Display dropdown box selected Value in Edit

Question

Hai Friends
          I m creating one sample application in my fields of my application are
Name:(Textbox),
class:(dropdown box)
add(button)
after press the add button entire details ll shown in gridview's with edit & delete.
now my problem is when choose edit means(Ex: i entered student name like 'ram' class '10th' in gridview if i m press edit the dropdown doesn't show the '10th') ll show in starting value.
i need display only selected value of dropdown where i m selected value doing edit.

Thanks & regrds
Rocky