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Trying to add ajax TabContainer, getting error "The Controls collection cannot be modified because the control contains code blocks (i.e. <% ... %>)."

Answer 1

+1 A:

This error is not specific to Ajax.

You could try putting your ajax:TabContainer inside an asp:Panel. Alternatively, remove the <% ...%> code blocks from your page.

Joe 2008-12-10 18:57:29

There are no <% %> code blocks in my page! Furthermore, in the sample website, the TabContainer wasn't in an asp:Panel.

Cybis 2008-12-10 19:03:55

Answer 2

+1 A:

I've figured it out!

This is the error message you get if you attempt to use AJAX controls while your < head > contains a < script > tag.

I just moved the javascript into the body, and it seems to work fine now.

Cybis 2008-12-10 20:57:14

WOW THANKS!!! I really, really hated this error. "The Controls collection cannot be modified because the control contains code blocks" What the hell is that supposed to mean!?

wallyqs 2009-03-18 20:15:57

Answer 3

+4 A:

You can't use <%= %> (write) blocks inside a control that uses the standard server rendering - you get this error.

In order for the ASP AJAX components to work you need:

<head runat="server">...

Otherwise it crashes with this error too.

However you can databind inside these server controls:

<head runat="server">
    <link rel="stylesheet" type="text/css" 
        href="<%# ResolveUrl( "~/styles/common.aspx" ) %>" />
...

And then in your page load:

Page.Header.DataBind();

The error occurs due to the way ASP WebForms render controls as component collections - they can handle either the collection (and expect databind <%#) or literal writes (and expect <%=) but not both together.

The best way to avoid this issue permanently is to switch to ASP MVC.

Keith 2009-06-29 13:21:31

Accepted answer changed, considering you're the first to actually answer the question correctly. Thank you! However, there's no need for me to learn ASP.NET MVC now. I lost my job recently. Probably a good thing in the long run though, I can't stand web development anymore.

Cybis 2009-07-04 05:18:23

Answer 4

A:

Pragnesh, Check between the HEAD tags for any javascript. I had some javascript with the <%%> code-blocks that prevented the AJAX tab controls from working.

MAbraham1 2010-02-04 15:43:03

Answer 5

A:

Hey guys, it's again not just javascript tags, but anything within the head tags of your page that uses <%= %> or <% Response.Write %>. Either change your code to use the databinding directive <%# eval(some code) %> or move the stuff to the body (this is also useful for speeding up the loading time of your pages).

Mavusi 2010-10-25 08:58:02

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Trying to add ajax TabContainer, getting error "The Controls collection cannot be modified because the control contains code blocks (i.e. <% ... %>)."

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