RadGrid insine UserControl makes the UserControl "not a known element"

[Heikki Heikkinen]

I ran into an interesting issue with the RadGrid.
I wanted to add a RadGrid into a UserControl and then add this UserControl to an aspx page. As soon as I add a RadGrid into the UserControl VisualStudio 2010 underlines the user control declaration on the page and when you hover on it to see what the problem is there is an error message: "Element 'TheUserControl' is not a known element. This can occuur when there is a compilation error in the Web site, or the web.config file is missing."

The page compiles and runs fine and the web.config file is not missing. Do you know what could be causing this?

[Tsvetina]

Hi Heikki,

You can try registering the UserControl in the controls section of your web.config file:

<?xml version="1.0"?>
<configuration>
  <system.web>
    <pages>
      <controls>
        <add tagPrefix="UserControlTagPrefix" src="~/Controls/UserControl.ascx" tagName="UserControl"/>
      </controls>
    </pages>
  </system.web>
</configuration>

Please, let us know if the issue persists after doing so.

Kind regards,
Tsvetina
the Telerik team

[Heikki Heikkinen]

This did not help. This is not a critical problem since everything compiles and runs just fine.

PS. I added a RadCodeBlock to my other UserControl that didn't have this problem. After adding the RadCodeBlock this same issue appeared with that UserControl.

[Tsvetina]

Hi Heikki,

This is usually caused by some inconsistency in assembly refrences. Check if there are references to any older versions.

Also, does the warning occur after performing a drag-and-drop of a control from the Visual Studio Toolbox? It could be that the ToolBox is populated with controls from a Telerik.Web.UI assembly, having a different version than the one in the project's BIN folder.

Additionally, there are a few other forum threads discussing the same issue with different reasons for the warnings. Here are links to two of them with the most possible solutions mentioned (if you search in the forum, more will show up):
Element '[xxx]' is not a known element
RadGrid is Not a Known Element Error


Best wishes,
Tsvetina
the Telerik team