Friday, August 24, 2007

The Controls collection cannot be modified because the control contains code blocks

Another day, another issue ;)

This had me going around in circles for a while until I realised what it was, if you're getting this error you can bet your bottom dollar that you have <%= %> somewhere in your page's header -furthermore I'd hazard a guess that you've got it in some JavaScript to reference an ASP.Net control on the page- and then you're trying to add a control to the header programmatically (or a custom control from someone like Telerik is trying to). Am I right¹?

¹ I'm not allowed to ask you to so I won't, but if I was right, then spend that bottom dollar clicking on one of the Google Ads :P

I can't tell you exactly why this occurs but my understanding of it is that ASP.Net can't re-create the header if it has Response.Write somewhere in the header (<%=) -most likely due to when the header is created it's not available (will look into it). No doubt you want to know the fix?

The Fix
The fix is simple, remove the inline code blocks and JavaScript and move it to your code behind i.e.:

string _manageSearch = String.Format(@'...'"lblFindAGift"");

string _manageSearch = String.Format( @" 
        function ManageSearch(){{
                var lbl = document.getElementById(""lblFindAGift"");
                var txt = document.getElementById(""{0}"");
                var btn = document.getElementById(""{1}"");

                .Do Something with it..

        }}",
        txtSearch.ClientID);

this.Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "ManageSearch", _manageSearch, true);

Remember: You need to escape the curly brackets otherwise you will get a "String.Format- Exception of type System.Web.HttpUnhandledException was thrown"

Update: Thanks to Julian Voelcker for sending me this alternative "fix" for the problem, can't say I like it though ;) basically instead of using <%= ... %> you would write the databinding expression of: <%# ... %>

The Controls collection cannot be modified because the control contains code blocks

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Tags: ASP.Net | C# | Web Development Tracked by:
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Wednesday, February 20, 2008 7:31:07 AM (GMT Standard Time, UTC+00:00)

Thanx a lotttt buddy...
This trick works :)

Happy Programming....

Kailash Dhondiyal

Monday, May 19, 2008 5:07:37 PM (GMT Daylight Time, UTC+01:00)

I am getting this error when trying to use the following code in the head section of a masterpage:
<!--[if lte IE 7]>
<style type="text/css"> @import url('<%= ResolveUrl("~/CSS/fieldset-styling-ie.css") %>;') </style>
<![endif]-->

OutOfTouch

Saturday, January 17, 2009 2:17:00 PM (GMT Standard Time, UTC+00:00)

to solve this problem just remove the skin from this page
<pages theme=""

sample web.config
<location path="Forms">
<system.web>
<pages theme="" />
</system.web>
</location>

Tarek El-Mallah

Saturday, January 17, 2009 7:09:41 PM (GMT Standard Time, UTC+00:00)

Thanks Tarek however there are no themes on the page. This error relates to using the string replacement placeholders (the {}'s).

Tim

Tim

Sunday, June 21, 2009 11:50:45 AM (GMT Daylight Time, UTC+01:00)

Good Client Side Validation In Java Script

Sanjay Gupta

Friday, July 17, 2009 7:25:23 AM (GMT Daylight Time, UTC+01:00)

If you came here with the same problem that "outoftouch" has, then here's the solution:
(You don't need the resolveUrl method if using runat="server" on the head tag)
http://www.dailycoding.com/Posts/the_script_tag_runatserver_problem_solution_using_resolveurl.aspx

krishna