I'm getting three similar errors when trying to compile a BlogEngine 2.6 Web Application Project:
In VS intellisense:
the type 'RazorHelpers' exists in both 'App_Code' and BlogEngine.Web.dll
Compile error:
Error 27 The type 'RazorHelpers' exists in both
'C:\inetpub\wwwroot\Nordic\Bin\BlogEngine.Web.dll' and 'App_Code'
c:\inetpub\wwwroot\Nordic\themes\RazorHost\CommentView.ascx 25
Eventually, I had to abandon the 2.6 WAP version and switch to the Website version, then migrate all of my design and code customizations.