Could not load file or assembly Newtonsoft.json - error 0x80131040


strong textGood day,

I develop applications on the customer's server. There are several projects one of them is in ASP.NET.

And suddenly this error appeared.


There was no change between launches.

I compared all versions of the Newtonsoft.json library to version, I compared all versions of .NET to 4.5.

I have reinstalled the Newtonsoft.json library several times on all projects. Using the command line in Visual Studio.

Unfortunately, the error still appears.

The funny thing is that the same error is shown both in this project and in another where there were no changes and they are not related to each other (another solutin, another project, another database, the first is in GIT and the second in TFS) only same develp server(RDP)

Subsequently, I tried to change the version of the Newtonsoft.json library to version but the error remained the same and again with version !!

What else could be the problem? I googleed and found something like GAC. But I didn't quite understand how it works? How can I find where the problem is? How to solve it? Some ideas?
asked on Stack Overflow Nov 1, 2020 by Pavel Kučera

1 Answer


So that's a really funny story.

After a day of reinstalling, removing, and finding context, I created a new project in ASP, added a new project (worked), added an old project (didn't work), but the browser always crashed with an error on IIS Express. So I changed the port and ABRAKADABRA's website started.

The hypothesis is that if more people are working on the desktop and running the project under the same port, it is possible that there is a problem with the references and they then refer elsewhere and cause the error.

Especially if users tend to leave VS open and therefore IIS Express

Helped change ports for individual developer.

But honestly, I have not found a similar solution to the problem anywhere.

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answered on Stack Overflow Nov 2, 2020 by Pavel Kučera

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