Unknown server tag

[Tim Runyan]

I'm using ASP.NET AJAX 2008.2.723. I am getting "unknown server tag" for every telerik control on the page (tabstrip & rotator). The controls are working in design mode, but when I build I get the server tag error. The register added to the page was

<%@ Register Assembly="Telerik.Web.UI" Namespace="Telerik.Web.UI" TagPrefix="telerik" %>

The BIN folder contains telerik.web.ui.dll (12,422kb), telerik.web.ui.dll.refresh (1kb), and telerik.web.ui.xml(2,909kb).

If the BIN files are there, and the Register is there, what else causes the telerik server tags to be unknown?

[Shinu]

Hi Tim,

If you get an error when you run the page, there may be a problem with your referenced assembly or your web.config. Make sure that the correct Telerik.Web.UI.dll is in your  Bin directory and make any references to the Telerik.Web.UI assembly in the web.config are configured for the correct version.

Thanks
Shinu.

[Tim Runyan]

Shinu, the dll was added to my BIN directory by VS when i dragged the controls onto my form. The tooltip in the VS tool box when I hover over the tabstrip control says "Version 2008.2.723.35 from Telerik.NET Component". When I hover over RadRotator the tooltip says "RadRotator".

I have never made any manual changes to the web.config. Just installed 2008.2.723, made a master page and a few content pages, dragged the tabstrip and rotator controls onto the master page (they work fine in design mode), then tried to build. The telerik prefix is unknown.

I thought that if the Register was on my master page where the controls are used no manual changes were required to the web.config. Is that correct?

The only instance of "telerik" i see in the web.config is the following:

<

add assembly="Telerik.Charting, Version=2.0.3.0, Culture=neutral, PublicKeyToken=D14F3DCC8E3E8763"/>

[Daniel]

Hello Tim

Please try to register your controls in web.config as shown below:

<system.web>
    <pages>
        <controls>
      <add tagPrefix="telerik" namespace="Telerik.Web.UI" assembly="Telerik.Web.UI"/>

Kind regards,
Daniel
the Telerik team

Check out Telerik Trainer, the state of the art learning tool for Telerik products.

[Tim Runyan]

Thanks Daniel. I pasted that line into my web.config but still get the "unknown server tag" build errors. What else might cause the telerik prefix to be unrecognized? Is there anything special about the fact that the controls are being used on a master page?

[Daniel]

Hello Tim,

Please try to delete the assembly references pointing to our RadControls and create them again. The needed steps are illustrated on the attached screenshots.

Regards,
Daniel
the Telerik team

Check out Telerik Trainer, the state of the art learning tool for Telerik products.

[Tim Runyan]

Daniel, VS is not displaying a references folder. So in VS I chose "Add reference" from the "Website" menu and browsed existing references. The only Telerik reference I saw was under the .NET tab and it was "Telerik.Charting" version 2.0.3.0. I did not remove this.

I followed your screen shots to add a reference to "Telerik.Web.UI.dll" from the BIN35 folder. That reference now shows on the "Recent" tab (but not on the .NET tab) as version 2008.2.723.35.

I still get the "unknown server tag" message. Did I correctly do what you were suggesting?

[Nate]

I've tried everything suggested in this article as well and and still no success.  Any more ideas.

The weird thing is i can uninstall then resintall telerik controls and it works fine for an undetermined amount of time(a few days), then breaks again.

TIA

[Daniel]

Hello Nate and Tim,

Could you please attach a simple working project through our support ticket system in order to examine the problem locally?

Regards,
Daniel
the Telerik team

Check out Telerik Trainer, the state of the art learning tool for Telerik products.

[Nate]

Actually, i tried adding Telerik.Charting.dll to my references and that took care of the Unknow Server tag html error.  Thanks!

[Richie]

Hi,
Try adding any random control, and than click on the design part in order to update what you see.
This simple action made all "unknown tags" errors disappear and after that I just removed the random control and life was beautiful again:-)

I know this stupid action might sound , well.. stupid, but after searching the web, trying to understand what GAC means, and spending many hours trying to resolve that - this just helped me.

Everything I write from here is in order to hopefully help google searchers to find this solution in case they are in this situation - so you can avoid reading that.

I use visual studio 2010, asp.net 4, and I got that "unknown server tag" after upgrading radcontrols.
Many forums I found in the web directed me to find solutions related to GAC which I personaaly still don't understand.
I got those links to the rescue but with no luck. :
1. http://www.telerik.com/help/aspnet-ajax/introduction-design-time-troubleshooting.html
2. http://www.telerik.com/help/aspnet-ajax/introduction-add-to-global-assembly-cache.html

And I just hope that if this solution (which I wrote in the begining) helped one person some where in the world - I will be glad!!! :-)
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[Hristo Valyavicharski]

Hi Richie,

Make sure that you have added a reference to Telerik.Web.UI.dll to your project and add a register page directive:

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="Default" %>
<%@ Register Assembly="Telerik.Web.UI" Namespace="Telerik.Web.UI" TagPrefix="telerik" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
    <telerik:RadStyleSheetManager ID="RadStyleSheetManager1" runat="server" />
</head>
<body>

or add a controls section in your web.config:

<?xml version="1.0"?>
<configuration>
    <appSettings>
        <add key="Telerik.ScriptManager.TelerikCdn" value="Disabled" />
        <add key="Telerik.StyleSheetManager.TelerikCdn" value="Disabled" />
    </appSettings>
    <system.web>
        <compilation debug="false" targetFramework="4.5" />
        <httpRuntime targetFramework="4.5" />
        <pages>
            <controls>
                <add tagPrefix="telerik" namespace="Telerik.Web.UI" assembly="Telerik.Web.UI" />
            </controls>
        </pages>
        <httpHandlers>

Regards,
Hristo Valyavicharski
Telerik

[Richie]

Hi,
Thank you very much but I currently don't have the problem.
In any case - when I had the problem - I took care of both things you mentioned:
dll files were updated
web.config was updated as well
and it didn't solve the problem.
The simple action of adding and removing a control was magically what solved the problem for me :-)