can't get selected state of a items of asp.net checked list box while mannul post back.

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C#

ASP.NET

jQuery

jQuery-UI

function CountrySelect(uniqueID) {

           var dialog_buttons = {};
           dialog_buttons['Save'] = function () { __doPostBack('chkcountries', ''); }

           $(document).ready(function () {
               $(function () {
                   var dlg = $("#dialog").dialog({
                       maxWidth: 400,
                       maxHeight: 500,
                       width: 400,
                       height: 500,

                       autoOpen: false,
                       modal: true,
                       buttons:dialog_buttons,
                       title:"Country Selection dialog",
                       close: CloseFunction
                       ,
                       show: {
                           effect: "Clip",
                           duration: 1000
                       },
                       hide: {
                           effect: "fade",
                           duration: 1000
                       }
                   });

                   dlg.dialog('open');

                   function CloseFunction() {
                       __doPostBack('logout', '');
                   };
               });

           });

       }

and markup for div with id dialog is

<div id="dialog" style="display:none">
            <p>Select Countries</p>
            <p>
                <asp:CheckBoxList ID="chkcountries"  runat="server">                   
                </asp:CheckBoxList>
            </p>
        </div>

and in cs file code is

foreach (ListItem val in chkcountries.Items)
             {
                 if (val.Selected == true)
                 {

                 }
             }

problem is on postback it says no item is checked. why

val.selected=false

always