The 'X is undefined' error occurs or extensions are rendered with incorrect styles

• Oct 06, 2023
• 2 minutes to read

Possible Errors:

• “‘aspx***’ is undefined”

• “ASPxClient*** is undefined”

• The default styles/images/scripts for DevExpress ASP.NET MVC extensions are not loaded.

Solution:

Check the following to solve this issue:

1. Make sure the ASPxHttpHandlerModule is registered in Web.config.

   The ASPxHttpHandlerModule allows DevExpress ASP.NET MVC extensions to load their resources. The Web.config file should contain a reference to this module in the system.web/httpModules and system.webServer/modules (for IIS7 in integrated mode) sections.

   IIS (classic mode)

   XML

   <system.web>  
       <httpHandlers>  
       <add type="DevExpress.Web.ASPxHttpHandlerModule, DevExpress.Web.vX.Y, Version=X.Y.Z.0, Culture=neutral, PublicKeyToken=b88d1754d700e49a" verb="GET"  
       path="DX.ashx" validate="false" />  
       </httpHandlers>  
       <httpModules>  
       <add type="DevExpress.Web.ASPxHttpHandlerModule, DevExpress.Web.vX.Y, Version=X.Y.Z.0, Culture=neutral, PublicKeyToken=b88d1754d700e49a" name="ASPxHttpHandlerModule"/>  
       </httpModules>  
   </system.web>  
   

   IIS7 (integrated mode)

   XML

   <system.web>  
       <httpHandlers>  
           <add type="DevExpress.Web.ASPxHttpHandlerModule, DevExpress.Web.vX.Y, Version=X.Y.Z.0, Culture=neutral, PublicKeyToken=b88d1754d700e49a" verb="GET"  
           path="DX.ashx" validate="false" />  
       </httpHandlers>  
       <httpModules>  
   
       </httpModules>  
   </system.web>  
   
   <system.webServer>  
       <validation validateIntegratedModeConfiguration="false" />  
       <handlers>  
           <add type="DevExpress.Web.ASPxHttpHandlerModule, DevExpress.Web.vX.Y, Version=X.Y.Z.0, Culture=neutral, PublicKeyToken=b88d1754d700e49a" verb="GET" name="ASPxHttpHandlerModule"  
           path="DX.ashx" preCondition="integratedMode" />  
       </handlers>  
       <modules>  
           <add type="DevExpress.Web.ASPxHttpHandlerModule, DevExpress.Web.vX.Y, Version=X.Y.Z.0, Culture=neutral, PublicKeyToken=b88d1754d700e49a" name="ASPxHttpHandlerModule"/>  
       </modules>  
   </system.webServer>
   

2. Make sure the application’s folder is marked as a separate IIS application.

3. Add “Full control“ permission for the “IIS_IUSRS“ account in the application folder.

4. Rewrite URL. Add an exception for the DXR.axd URL if you specify a Rewrite URL rule in your Proxy Layer/URL Rewrite Module that blocks/rewrites requests from resource handlers:

   • WebResource.axd (for standard handlers);
   • DXR.axd (for the DevExpresss ASPxHttpHandlerModule).

See Also:

• How To: resolve the “Cannot add duplicate collection entry of type ‘add’ with unique key attribute ‘name’ set to ‘ASPxHttpHandlerModule’” error