'Uncaught TypeError: DevExpress.assertDevExtremeVersion is not a function' error occurs

• Jul 08, 2025

This section explains the error, and lists steps needed to diagnose and resolve it. If these direction do not help solve your error, submit a ticket in our Support Center.

Issue

The following error appears in the console after an ASP.NET Core project with DevExtreme components is upgraded to v24.1 or later: “Uncaught TypeError: DevExpress.assertDevExtremeVersion is not a function”.

Solution

Since this error occurs when the dx.all.js script is out of date, you must confirm the DevExtreme.AspNet.Core NuGet package version in your project. Replace dx.all.js with the matching version (v24.1 or later).

Update all scripts and CSS files in the project. Copy files from the installation directory:

C:\Program Files\DevExpress 25.2\DevExtreme\Sources\Lib