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Use Telerik Controls with ScriptManager on Login Page Throws an Error


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When working with Telerik UI for ASP.NET AJAX, using the Telerik controls with the ScriptManager on my login page throws an error.

Error Messages

  • ASP.NET Ajax client-side framework failed to load

  • 'Sys' is undefined

  • "Telerik.Web.UI" is undefined


As the website denies access to all pages to unauthorized users, access to the Telerik.Web.UI.WebResource.axd handler is unauthorized and the handler serves the content of the login page instead of the combined scripts.

Alternatively, if a website was migrated from a previous ASP.NET version to the latest, a preCondition attribute might have been added to the Telerik.Web.UI.WebResource.axd handler declaration stating that the runtime version is 2.0:



Depending on the possible cause of this issue, use either of the following approaches:

  • (Unauthorized handler) Add a <location> section to the application configuration file thus allowing access to Telerik.Web.UI.WebResource.axd to all users, for example:

    <location path="Telerik.Web.UI.WebResource.axd">
            <allow users="*"/>
  • (Previous version) Remove runtimeVersionv2.0 from the handler declaration.
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