Could not load file or assembly System Version 4 0 0 0 Culture neutral PublicKeyToken b77a5c561934e089 or one of its dependencies

Question

I have this exception generated on some user machines   1 of 20    Could not load file or assembly  System  Version 4 0 0 0  Culture neutral  PublicKeyToken b77a5c561934e089  or one of its dependencies  The system cannot find the file specified   I found several references to this error over the web and this site but nothing helped  I have an add-in application which uses WCF to connect to the server  The add-in built with  NET Framework 3 5 with VS 2008  The error is reproducible on one of the test machines in only one user account  I install my application and can only reproduce this from one account on this machine everywhere else it is working fine  Furthermore it is only reproducible with only one version of host application which I created add-in for  I assume because it uses differnet  NET Frameworks   I have checked the fuse logs and I see the following   Assembly manager loaded from   C  Windows Microsoft NET Framework64 v2 0 50727 mscorwks dll Running under executable  C  Program Files SolidWorks Corp SolidWorks sldworks exe --- A detailed error log follows        Pre-bind state information     LOG  User   Home User LOG  DisplayName   System  Version 4 0 0 0  Culture neutral  PublicKeyToken b77a5c561934e089   Fully-specified  LOG  Appbase   file    C  Program Files SolidWorks Corp SolidWorks  LOG  Initial PrivatePath   NULL LOG  Dynamic Base   NULL LOG  Cache Base   NULL LOG  AppName   NULL Calling assembly   System Configuration  Version 2 0 0 0  Culture neutral  PublicKeyToken b03f5f7f11d50a3a    So by some reasons it is trying to use v2 0 50727 mscorwks dll loader to load the Version 4 0 0 0 of System dll  On build machine I m referring 2 0 0 0 version of System dll

User · Answer

I had this same problem - some users could pull from git and everything ran fine. Some would pull and get a very similar exception:

Could not load file or assembly '..., Version=..., Culture=neutral, PublicKeyToken=...' or one of its dependencies. The system cannot find the file specified.

In my particular case it was AjaxMin, so the actual error looked like this but the details don't matter:

Could not load file or assembly 'AjaxMin, Version=4.95.4924.12383, Culture=neutral, PublicKeyToken=21ef50ce11b5d80f' or one of its dependencies. The system cannot find the file specified.

It turned out to be a result of the following actions on a Solution:

NuGet Package Restore was turned on for the Solution.
A Project was added, and a Nuget package was installed into it (AjaxMin in this case).
The Project was moved to different folder in the Solution.
The Nuget package was updated to a newer version.

And slowly but surely this bug started showing up for some users.

The reason was the Solution-level packages/respositories.config kept the old Project reference, and now had a new, second entry for the moved Project. In other words it had this before the reorg:

  <repository path="..\Old\packages.config" />

And this after the reorg:

  <repository path="..\Old\packages.config" />
  <repository path="..\New\packages.config" />

So the first line now refers to a Project that, while on disk, is no longer part of my Solution.

With Nuget Package Restore on, both packages.config files were being read, which each pointed to their own list of Nuget packages and package versions. Until a Nuget package was updated to a newer version however, there weren't any conflicts.

Once a Nuget package was updated, however, only active Projects had their repositories listings updated. NuGet Package Restore chose to download just one version of the library - the first one it encountered in repositories.config, which was the older one. The compiler and IDE proceeded as though it chose the newer one. The result was a run-time exception saying the DLL was missing.

The answer obviously is to delete any lines from this file that referenced Projects that aren't in your Solution.

User · Answer

I ve seen this a couple times  and it is usually fixed by running a repair on  NET Framework  whichever version the application is trying to use

User · Answer

In my case  I was able to find issue with ScriptManager by setting Debug true in web config file

User · Answer

You can enable NuGet packages and update you dlls  so that it work  or you can update the package manually by going through the package manager in your vs if u know which version you require for your solution

User · Answer

Even I have experience some more strange things  I can see there is no dll in GAC from where the dll is loading but windows   Module shows system dll version 4 0 0 0 loaded

User · Answer

I got this after downgrading a project from  net 4 5 to  net 3 5   To resolve I had to go in to the project - properties - settings window and delete all my settings  save the project  exit and restart visual studio  go back into project - properties -settings window and re-enter all my settings and their default values

User · Answer

This worked for me  Go to Project- Propertied- Target Frawork- Change frame work like 3 5 to 4 0

User · Answer

i just changed my target  net framework and it worked  in my case i changed from  net 4 7 to  net 4  Right click your solution and select properties selct properties Click Application  gt  gt  Target Framework

User · Answer

I answered too late but it has worked in my case If you are facing this issue in your project please add the following line in your web config     lt compilation  batch  false   gt    This worked in my case  If you already have compilation tag in your web config then add only batch  false  property to it

User · Answer

I had the problem under Linux and I needed to install those  I don t know which one actually fixed the problem  but that error was gone after that   apt-get install mono-utils mono-runtime-sgen mono-runtime-common                   mono-runtime-boehm mono-runtime-dbg mono-xbuild

User · Answer

You are using  net 4  - Maybe on the clients there is only the   net framework 4 client profile  installed  Try to install full package   Download here

[c#] Could not load file or assembly 'System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' or one of its dependencies

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