gridview row

Question

i aI have web page in this this page i use gridview and in this gridview i have textbox. Now i want  to add new row using dropdown list value.and this dropdownlist  out side the gridview.

like i wnat to add 2 row in grideview i select value from dropdownlist of  list box is 2 and add 2 rows in gridview  please give me suggest or give me code for this.