checkbox unchecked after page refresh if updatepanel used

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ASP.NET

I used asp:update panel a

<asp:UpdatePanel ID="GetUpdDet"  runat="server" UpdateMode="Conditional">
  <ContentTemplate>

<asp:CheckBoxList ID="chkCountries" runat="server" AutoPostBack="true"  OnSelectedIndexChanged="Country_Selected">
                                <asp:ListItem Text="rating 5" Value="5"><span class="Fivestar_ft"></span></asp:ListItem>
                                <asp:ListItem Text="rating 4" Value="4"><span class="Fourstar_ft"></span></asp:ListItem>
                                <asp:ListItem Text="rating 3" Value="3"><span class="Threestar_ft"></span></asp:ListItem>
                                <asp:ListItem Text="rating 2" Value="2"><span class="Twostar_ft"></span></asp:ListItem>
                            </asp:CheckBoxList>

<asp:listview ID="ProductListList" runat="server" >

</ContentTemplate>
         </asp:UpdatePanel>

in above if i click checkbox , i call OnSelectedIndexChanged="Country_Selected" function, and filter listview and listview.datasource and databind
, and updatepanelid.update();


in page_load , i use

if (!ispostback) listview.datasource and databind

but , when i click checkbox , page doesnot refresh and i see filtered value in listview , then when i refresh page manually, checkbox is unchecked , and listview shown is original without filters..

pls advice, what to do to keep checkbox as checked ,and gridview filtered , when page refresh with updatepanel ,