vb.net - Datagridview Check Box Error Default -

i have datagridview in user input data shifts have worked. have checkbox tick whether require on call payment shift. it's unchecked value "n" , when checked value "y". works well.

however when user leaves check box @ it's default state load, when come send database exception. how can default value "n" if user hasn't altered box?

error message: object reference not set instance of object.

you need declare checkbox in datagrid item_databound

     private sub datagrid_itemdatabound(byval sender object, byval e system.web.ui.webcontrols.datagriditemeventargs) handles datagrid.itemdatabound              if (e.item.itemtype = listitemtype.item) or (e.item.itemtype = listitemtype.alternatingitem)                dim checkbox checkbox = e.item.findcontrol("yourcheckboxid")             end if      end sub