asp.net mvc drop down list multiple option

[HamidSeyfi]

i am using drop down list with multiple option in asp.net mvc with html.helper (@Html.DropDownListFor)
when i post the page from client to server , i get data as int[] in client and every thing is ok
when i want to send data from client to server, and i send selected options as (int[]) to client
the drop down list control does not show selected options and it is empty