nested datalist with select all check box in parent and nested datalist

Hi I have nested datalist. After going through couple of forums I could successfully implement this. But I have a checkbox in parent datalist to select all sub items and also a check box in nested datalist to select individual sub items. I have written cbxSelectAll_CheckedChanged to check all sub items when a prent checkbox is checked. It works fine for the first time but 2nd time as the page postsback it does not retain the previously selected items. I tried using update panel but nothing works. Any help on this please |       
<asp:DataList ID="dlAlphabetPage" runat="server" cssClass="alphabetList" OnItemCommand="dlAlphabetPage_ItemCommand"                             OnItemDataBound="dlAlphabetPage_ItemDataBound" RepeatDirection="Horizontal&qu ...