itemtemplate dropdownlist not binding based on first itemtemplate

hi..
i have two item template which consist two dropdownlist D1,D2...
here what im doing is d2 is binding based d1 selected value...
im using this code in D1_Selectedindexchanged

 foreach (GridViewRow row in Gridview1.Rows)         {             DropDownList D2 = (DropDownList)row.FindControl("DropDownList1");             DropDownLi ...