We recently revamped our source control, continuous integration, and bug tracking solution at OrcsWeb to take advantage of Git. Part of the solution includes a build server that automatically runs tests against projects and, assuming they pass, packages the and deploys the application using Web Deploy. Several of the projects typically include NuGet packages, and a new feature of NuGet (as of 1.6 & 2.0) allows you to exclude these NuGet packages when committing to source control. By enabling package restore, NuGet will automatically download any packages from packages.config on any system where they’re missing.

After uploading a new MVC 4 project that was using this NuGet Package Restore functionality, I was receiving the YSOD that asp.net “Could not load file or assembly ‘Newtonsoft.Jason, Version=4.5.0.0′”. I confirmed that NuGet was downloading the packages on the build server, but for some reason it wasn’t being included in the deployment. BlackSpy’s solution for the Newtonsoft.Json error on stackoverflow.com fixed the issue for me as well.

I removed the entry for Newtonsoft.Json version 4.5.6 from packages.config, saved and built the project, then re-added Newtonsoft.Json 4.5.11 from NuGet and committed the changes. The build server picked up the updates, downloaded the missing package, and deployed it to the server.