The call is ambiguous between the following methods or properties: 'DevExpress.Web.Mvc.UI.HtmlHelperExtension.DevExpress(System.Web.Mvc.HtmlHelper)

Solution:

It appears that older versions of DevExpress assemblies have been cached and now they conflict with the newly installed assemblies.  Please follow these steps, which should help you overcome the problem:

1. Close VS.

2. Restart your IIS or better yet, restart the "World Wide Web Publishing" service (Start menu\Settings\Control Panel\Administrative tools\Services).

3. Clear the "C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files\" and "C:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\" folders.

4. Clear the project's Bin and Obj folders.

5. Rebuild your application.

 

Please refer to : https://www.devexpress.com/Support/Center/Question/Details/Q348002