c# - Checkbox state not changed on postback -

i have following mark user control (.ascx)

<table> <tr>     <td>         <asp:label id="label1" runat="server" text="select logical symbol search:"></asp:label>     </td>     <td>         <asp:dropdownlist id="ddlcomponenttype" runat="server"              onselectedindexchanged="ddlcomponenttype_selectedindexchanged" autopostback="true">         </asp:dropdownlist>     </td>     <td>         <asp:checkbox id="chkadvsearchalllibs" runat="server" tooltip="check box search available libraries" text="search libraries"/>     </td> </tr> <tr>     <td>         <asp:label id="label2" runat="server" text="search logical symbol properties:"></asp:label>     </td>     <td>     </td> </tr> 

on page load

protected void page_load(object sender, eventargs e) {      searchresults(ref attributesearch, comptypeid); } 

where searchresults is

 private void searchresults(ref string attributesearch, int comptypeid)     {         datatable dtresults = this.advancedsearchcontrol.getsearchresults(ref attributesearch, comptypeid);     } 

and in usercontrol.ascx.cs

public datatable getsearchresults(ref string _attrvals, int comptypeid) {                 //other logic goes here                 ienumerable<model.componentinfo.componenttype> comptyperesult = comptypes in bllibrary.getcomponenttypebasedonlib(this.currentlibraryid, this.currentlibrary, this.chkadvsearchalllibs.checked) select comptypes.value; } 

this.chkadvsearchalllibs.checked false no matter if check-box checked on page , posted or not.

server side:

add autopostback="true" checkbox. it's not posting back.

client side:

<asp:checkbox runat="server" id="cb" onclick="checkboxchanged(this);" />  function checkboxchanged( sender ) { if ( sender.checked ) {         // clicked , checked     } else {         // clicked , unchecked     } }