Expanding ClientID in an event string - asp.net

Question

I'm having a problem with <%= obj.ClientID %> expansion, in a .ascx user control.
I have a .js file, containing a javascript function:
function doSomething(objectId)
{
...
}
I have a .ascx file, with some html elements, and in one element's onclick= I want to call doSomething(), passing the ID of an element in that .ascx file, where the passed ID is of an element other than the one being clicked on, so I can't use "this.".
Maybe it'd be clearer with an example.
This works:
<script type="text/javascript">
function redirect()
{
doSomething('<%= top.ClientID %>');
}
</script>
<div id="top" runat="server">
<img src="..." alt="..." onclick="redirect();"/>
</div>
But this does not:
<div id="top" runat="server">
<img src="..." alt="..." onclick="doSomething('<%= top.ClientID %>');"/>
</div>
When I look at the source, I see that the <%= %> substitution has not happened, instead of "doSomething('ctl00_myControl_top');" I get "doSomething('<%= top.ClientID %>');"
For some reason, the script expansion happens in the former case, but not in the latter. The work-around, of course, is not acceptable because it will break if I include multiple copies of the control on a page - only one instance's "redirect()" function will be accessible.
Any ideas on how to make this substitution work?

Answer 1

Works on my machine?
<div id="top" runat="server">
rarrarara
</div>
Becomes
<div id="ctl00_ContentPlaceHolder1_top">
rarrarara
</div>

Answer 2

Consider an alternate route:
Ensure that the control you are referencing in JavaScript using the inline expression <%= (controlName).ClientID %> has its 'ClientIDMode' specifier set to a static value and then simply use the text in the ID field of that control to refer to it. I ended up using this in a recent project it works great. Please see the link below for a more detailed explanation:
Code Project - ASP.NET v4.0 Client ID Feature
Along with setting the 'ClientIDMode' specifier to "Static", I found a useful idea regarding placing text from a global resource file (in the case of language switching) into a field of a standard HTML control that does not have to run at the server level. I used this on a standard HTML button that was supposed to call a JavaScript function that would show/hide a specific div or ASP Panel. Use the GlobalResource function in the inline expression tags like so:
<input id="btnToggleFilterOptions" type="button" value="<%=GetGlobalResourceObject("SiteResource", "btnToggleFilterOption")%>" onclick="javascript:ToggleCssClass('divFilterOption','visible'); return false;" class="button submit" />
<asp:Panel ID="divFilterOption" ClientIDMode="Static" runat="server">
<asp:TextBox ID="txtFilterOption1" runat="server" />
</asp:Panel>
I know this is an old post, but it is a popular hit when searching on Google for Asp .NET and ClientID. I hope this helps somebody else out!