Adding row to the gridview

Question

hi all,
how can i add new row to the gridview without reload the old already created rows,because i have a gridview with 2 templete column one of them are dropdownlist ,when i create new row with the same critera the dropdown list in the first row reload from start and dont have the last selected value
so how can i create new row and the first row keep(stored) the value in it
how can i do that ?
thanks for advice