I was working on BugTracker.NET today and I started getting this error while trying to use a new package that I had added. The problem was that the library I added was referencing Newtonsoft.Json v4.5 while my application was using v6.0.
Now, this is a common problem that can normally be resolved by adding an assembly binding redirect that forces all assemblies to use the newer version of Newtonsoft.Json that your application is referencing. The solutions are well document over on StackOverflow.
Unfortunately, none of the solutions described on the internets worked for me. I was starting to think I was losing my mind when suddenly I noticed that I was getting 100s of warnings about the format of my web.config.
It seems that the xmlns attribute was causing some problems. I tried removing the offending xmlns attribute and everything started to work as expected. For some reason, this seemingly harmless xmlns attribute was causing .NET to ignore the binding redirects in my web.config.
….now if only I could get those 4 hours back.