ASP.NET Themes and required Head objects

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ASP.NET Themes and required Head objects

19 comments

March 03, 2006 @ 2:10 am

Hmmm… I'm creating an RSS Feed page on one of my new apps I'm working on (yet another Blog <g>)…

The site uses themes but when I'm generating the Rss.aspx page which looks like this:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Rss.aspx.cs"

Inherits="Westwind.WebLog.Rss"

EnableTheming="false" EnableSessionState="false" %>

But ASP.NET complains about the fact that the header is missing:

Exception Details: System.InvalidOperationException: Using themed css files requires a header control on the page. (e.g. <head runat="server" />).

This even though EnableTheming is off for the page.

In order to get this to work I have to drop in the HTML header like this:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Rss.aspx.cs"

Inherits="Westwind.WebLog.Rss"

EnableTheming="false" EnableSessionState="false" %>

It doesn't matter for my RSS page since the XML is generated directly into the Response.OutputStream(), but this adds a little unneeded overhead into the page. But if you had a page that wanted to use the ASPX content to generate some non-HTML output that doesn't include a header you'd have to explicitly set the header visible=false I guess.

So to generate a page that shows just your text and no header:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="WebLog.WebForm1" %>

<head runat="server" visible=false/>This is a test

I guess this is not a big deal, but seems like an oversight in the page parser.

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re: ASP.NET Themes and required Head objects
by Fredrik March 03, 2006 @ 3:00 am

The fact that you're using an aspx page and hijacking the output stream is a much bigger overhead in my opinion, - I'd recommend using an http handler instead :)

Also check out the new ASP.NET 2.0 RSS toolkit, which looks really sweet: http://weblogs.asp.net/scottgu/archive/2006/02/22/438738.aspx

re: ASP.NET Themes and required Head objects
by Mikael Söderström March 03, 2006 @ 3:17 am

I had the same problem while generating RSS and images on the fly, but using ashx instead of aspx solved the problems. :)

re: ASP.NET Themes and required Head objects
by Rick Strahl March 03, 2006 @ 9:47 am

Frederik,

No doubt and normally I would a handler but the site needs to match URLs as much as possible so hence the ASPX page. Hmmm... I guess I can stuff it into my Url Rewriting handler as well.

In either case this is isn't going to matter all that much since the RSS page will cached heavily anyway.

The main point is though that EnableTheming false should really remove this header requirement.

re: ASP.NET Themes and required Head objects
by Mark Zak June 20, 2006 @ 2:07 pm

You can actually get this working by setting the theme for that page to blank. ie:
<location path="CMS">
<system.web>
<pages theme="" />
</system.web>
</location>

I'm doing this in a few MCMS projects.

re: ASP.NET Themes and required Head objects
by Rick Strahl June 20, 2006 @ 3:44 pm

Mark yes you can turn the theme off, but that's usually not the desired behavior in bulk. But you can also turn the theme of in the page directive with Theme="". Note that EnableTheming="false" doesn't do the trick, which is a little silly...

re: ASP.NET Themes and required Head objects
by John R. Pattison August 15, 2006 @ 9:08 am

Thanks Rick! I ran into this exact problem this morning trying to put together a quick flat-file data feed for a client. I understand what everyone else is saying -- yes there are other ways you could do it -- but I agree with you that it is an oversight in the page parser.

re: ASP.NET Themes and required Head objects
by Alan September 22, 2006 @ 7:42 am

Thanks!

Worked great... I ran into this issue using a page with an XML doctype feeding an AJAX callback...

Appreciate the help!

re: ASP.NET Themes and required Head objects
by ernest November 02, 2006 @ 6:08 am

Thanks,
the page directive Theme="" works fine for me.

DotNetSlackers: ASP.NET Themes and required Head objects
by DotNetSlackers Latest ASP.NET News November 24, 2006 @ 6:01 am

re: ASP.NET Themes and required Head objects
by _Guanche- January 30, 2007 @ 1:30 am

Thanks much.

Doesnt make much sense to me that theme="" does the job when EnableTheming=false (which is docummented) doesnt.

re: ASP.NET Themes and required Head objects
by Chuck February 26, 2007 @ 5:29 pm

Awesome! Thanks for the tip; it worked great.

re: ASP.NET Themes and required Head objects
by Ryan Pfister March 09, 2007 @ 2:58 pm

I agree. Disabling theming using EnableTheming = "false" should fix the error. I came in from google searching for a solution to that exact problem (I got the "Using themed css files requires a header control on the page", then I turned disabled theming, but then still got the error).

re: ASP.NET Themes and required Head objects
by Ken Eldridge May 22, 2007 @ 11:27 am

This was the only thing that worked for me after Google'ing most of the morning. Just needed to feed by Ajax call.

re: ASP.NET Themes and required Head objects
by luu July 19, 2007 @ 2:16 pm

Thanks for the tips.

re: ASP.NET Themes and required Head objects
by Ozzie January 23, 2008 @ 3:08 am

thanks for the help guys...

Mark Zak's snippet worked for me.

re: ASP.NET Themes and required Head objects
by atx April 02, 2008 @ 4:54 am

This works for me:
EnableTheming="false" StylesheetTheme=""

The hidden <head> tag is not needed then.

re: ASP.NET Themes and required Head objects
by Victor Garcia October 01, 2008 @ 11:15 am

After an hour of dealing with this... the tip worked... like a charm...
And the last one.... from atx... even better.

re: ASP.NET Themes and required Head objects
by humbads October 07, 2008 @ 11:34 am

This also works for Infragistics ImagePipe.aspx pages, that contain a SecureImagePipe control.

re: ASP.NET Themes and required Head objects
by Axel November 04, 2008 @ 7:08 am

Thanx - saved my day!