Error with assemblies after upgrade from 7.0 to 7.1

We are trying to upgrade our 7.0 site to 7.1. The project upgrades successfully according to Sitefinity Project Manager 7.1.5200.0, however when we go run the project, it shows an error. The weird thing is we've tried to update different instances of our app, and the error is different each time.

Sometimes the error is "Could not load file or assembly 'Newtonsoft.Json' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. " and sometimes it's "Could not load file or assembly 'System.Net.Http' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. 

 We have brought NuGet packages into the solution for the Web API and for Newtonsoft, but I'm surprised this upgrade is having trouble with that.

Hello Glen,

It is possible that a components in your solution is looking for a different dll version (in your case Newtonsoft.Json), and this can be easily solved as described in this blog post: Avoid Version errors with Assembly Binding.

It is needed to add the assembly name, token and specify the new version number of the assembly to be used.

Hope this helps.

Regards,
Vassil Vassilev
Telerik