'Umbraco.Core.Models.IPublishedContent' does not contain a definition for 'GetPropertyValue' and no extension method 'GetPropertyValue' accepting a first argument of type 'Umbraco.Core.Models.IPublishedContent' could be found (are you missing a using directive or an assembly reference?) d:\wwwroot\AppData\courier\revisions_backup\Views\myfile.cshtml

I keep getting these errors for lot of pages in my application. These files are located under courier\revisions__backup\Views.... Are these files even needed as they are in courier?

I am trying to understand Umbraco and maintain a pre developed site.

Any help is greatly appreciated.