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 menuSettingsControl PanelAdministrative toolsServices).

3. Clear the "C:WINDOWSMicrosoft.NETFrameworkv2.0.50727Temporary ASP.NET Files" and "C:WindowsMicrosoft.NETFrameworkv4.0.30319Temporary 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

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原文地址：https://www.cnblogs.com/michelledawm/p/5977013.html