Could not load file or assembly 'WebGrease, Version=1.5.1.25624, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies

Question

I have an MVC4 Web API project. While running the service project I am getting an error

Could not load file or assembly \'WebGrease, Version=1.5.1.25624,

Answer 1

Oldie but goldie...

I was working on a MVC 5 project in Visual Studio 2013, and I had the same problem. We were using Visual SVN for the versioning and I was the only one in my team that had this problem.

The only thing that worked for me was this:

1. Uninstall Microsoft.AspNet.Web.Optimization
2. In Nuget command prompt run: install-package Microsoft.AspNet.Web.Optimization -Version 1.0.0

This will install an older version of Web.Optimization. The project was initially referencing version 1.1.0. The problem is not with WebGrease, but with the System.Web.Optimization.dll that is referencing an old, inexisting version of WebGrease.

When I ran the project, it worked, but I wanted to use the same package version as the rest of team. So, I tried to update but... the error returned...

After this, I deleted the project (again) and took it back from the SVN. To my surprize, it started to work... The thing is that I had deleted the project completely and took it from the SVN several times before this. I even took the dlls from a colleague because I thought that maybe I'm getting corrupted files from NuGet, but to no avail.

I hope this will help someone, someday.. with Visual Studio 2016 and MVC 8 :)