unrecognized tag prefix or device filter 'telerik'.

[Jaymie]

I realise that there are few topics concerning this issue, but mine seems to be different.

Here is some information.
I recently uninstalled all previous versions of RadControls for ASP.Net because I was getting conflicts between different versions and having some issues when trying to modify the site from my home machine. So, once I uninstalled everything, I installed the latest build of the rad controls hoping that that would fix any issues I was having.
My home machine works fine, but my work machine will not work. The rad controls are displayed on a page but with no styling and they do not actually work, but no errors are thrown when building the site.
The only thing is the unrecognized tag prefix green underline.

I have read that putting the Telerik.Charting.dll into the bin folder fixes this issue, but the only version of this DLL I have is from a cached version which resides here:

C:\Program Files\Telerik\Telerik Trainer\CachedAssemblies\RadControls for ASP.NET AJAX\Q1 2008\Bin

Using this dll causes my website to break. A 'ASP.NET Ajax client-side framework failed to load.' error is thrown.

There is no other version to this dll anywhere. Is there something I am missing or is there a new solution to this problem?

[Pavlina]

Hi Jaymie,

This error could be generated when you have not granted permissions for the Telerik.Web.UI.WebResource.axd http handler to all users (through the web.config file). Review the relevant section of this help topic for more details.

Kind regards,
Pavlina
the Telerik team

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[Martin]

(I know it's quite an old thread, but anyway, here's another possible solution for the problem)

In my case, the problem was caused by an old version of Telerik.Web.Design.dll in the bin folder of my web app. Once I deleted this dll the problem went away.

I'm only referencing Telerik.Web.UI.dll from my web app (via a .refresh file), but somehow/somewhen the old version of Telerik.Web.Design.dll was also added to the bin folder.

Hope this helps.

[hkdave95]

Hi

Just to say that Martin's solution solved my problem.

David

[Prateek]

I have opened two different projects on different windows... problem is one is working correctly and another one is not working..... the problem is still same. So is there any issue of web.config or any thing else.

[Pavlina]

Hi Prateek,

You can try replacing your web config file with the one I have attached and see if you will still receive the unrecognized tag prefix error.

Regards,
Pavlina
Telerik

 

 

[Prateek]

Hi Pavlina,

I have Replaced my web.config to yours sample web.config file. but the problem is still same.

[Pavlina]

Hello Prateek,

At this point I would recommend you to isolate the problem in a simple runnable project and send it to us via support ticket. Otherwise it would be hard to determine the cause of the issue you are facing.

Regards,
Pavlina
Telerik