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Docs > Troubleshooting > Server-Side Issues > An alert message with the HTML/JavaScript/CSS content appears when you use callback-aware extensions
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An alert message with the HTML/JavaScript/CSS content appears when you use callback-aware extensions
An extension with 'X' name is already rendered
'System.Web.WebPages.Html.HtmlHelper' does not contain a definition for 'DevExpress'
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Alert message with the HTML/JavaScript/CSS content appears when you use callback-aware extensions

Solution:

Do the following to solve the issue:

  • The SettingsBase.Name property value should be the same between callbacks.

  • Define extensions in a separate PartialView file without additional tags (for example, HTML markup, scripts).

  • Use the Html.Partial, Html.RenderPartial expression/code block or the Html.Action, Html.RenderAction that return the PartialViewResult to render the PartialView.

  • The action method (CallbackRouteValues.Action) should return the same PartialViewResult that contains the callback-aware extensions.