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

    • 2 minutes to read

    Possible Errors

    • “‘aspx***’ is undefined”

    • “ASPxClient*** is undefined”

    • The default styles/images/scripts for DevExpress ASP.NET controls 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 controls 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. Registration is automatic if you place a DevExpress control on a form in Design view or if you use Project Templates to create an application. You can register the module if you create controls at runtime.

      IIS (classic mode)

      <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)

      <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