Could not load file or assembly 'Newtonsoft.Json' or one of its dependencies. Manifest definition does not match the assembly reference

To solve this, I ensured all my projects used the same version by running the following command and checking the results:

update-package Newtonsoft.Json -reinstall

And, lastly I removed the following from my web.config:

  <dependentAssembly>
    <assemblyIdentity name="Newtonsoft.Json" publicKeyToken="30ad4fe6b2a6aeed" culture="neutral" />
    <bindingRedirect oldVersion="0.0.0.0-6.0.0.0" newVersion="6.0.0.0" />
  </dependentAssembly>

If you want to ensure all your Newtonsoft.Json packages are the same version, you can specify the version like so:

update-package Newtonsoft.Json -version 6.0.0 -reinstall

I am using Newtonsoft.Json v6.0.3, but this is what I had to do in my Web.config file:

<dependentAssembly>
        <assemblyIdentity name="Newtonsoft.Json" publicKeyToken="30ad4fe6b2a6aeed" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-4.5.0.0" newVersion="6.0.0.0" />
</dependentAssembly>

Note that even though I am using 6.0.3, I had to put in newVersion="6.0.0.0"

In my packages.config file I have:

<package id="Newtonsoft.Json" version="6.0.3" targetFramework="net45" />

I tried the following after having already ensured that my computer had the same version in all locations and that my projects were all pointing to the same reference path. I had also made sure that the binding of the old version was their and bound to the current version of dll that I had.

I work in an environment with a strict framework and the framework team often upset the versioning with the different dll's.

How I fixed this issue was to run the package manager console within visual studio (2013). From there I ran the following command:

update-package Newtonsoft.Json -reinstall

followed by

update-package Newtonsoft.Json

This went through and updated all of my config files and relevant project files. Forcing them all to the same version of the dll. Which was initially version 4.5 before updating again to get the latest.