Could not load file or assembly 'System.ValueTuple'

Question

I've got a VS2017 project that compiles to a DLL which is then called by an EXE written by someone else. Both projects target .Net Framework 4.6.2. I rewrote one of my DLL methods to return a tuple and also imported the associated NuGet package. When I compile the project it includes System.ValueTuple.dll in the output directory which is then deployed to other machines where my DLL is loaded and called by the EXE. But when the EXE attempts to call the method that returns a tuple it crashes:

Unexpected Error Could not load file or assembly 'System.ValueTuple, Version=4.0.1.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51' or one of its dependencies. The system cannot find the file specified.

I'm not understanding why it's not finding the file since it's in the same folder as my DLL. Apparently MS did not include this assembly in .Net Framework 4.6.2.

Note that my DLL is registered in Windows using a machine.config file. I'm guessing that if I also add System.ValueTuple.dll to this file it will work (haven't tried yet and not sure this is the best approach, especially long term.) Is there a better way, besides waiting for 4.6.3 and hoping it includes this assembly?

Orth

"Note that my DLL is registered in Windows using a machine.config file" - do you mean your DLL is being put in the GAC, but System.ValueTuple.dll isn't? I can see how that would cause problems. – Fernando

@JonSkeet Yes. But I was under the assumption that Windows will look for referenced DLLs in the same folder as the calling application, which in this case is my DLL. – Orth

The path of the DLL never plays a role to find assemblies, only the startup EXE. – Schreiner

ValueTuple is built into .NET Framework 4.7, which was just announced and will be released shortly. That said, I don't understand why you ran into a problem with 4.6.2, since you imported the ValueTuple package from nuget. I'm not an expert at assembly binding, but your solution (below) worries me. Feel free to file an issue on the rolsyn repo with a small repro project (zipped). – Vedi

I ran into the same problem after updating (seemingly un-related) Nuget packages. Upgrading to 4.7.2 resolved the issue, but I also had to remove binding references. – Aquarium

It is funny but I faced same problem again after downgrade System.ValueTuple assambly and just comment out System.ValueTuple dependentAssembly section under runtime > assemblyBinding in web.config file. and now it is working. – Kisser

Answer 1

I resolved this issue by registering System.ValueTuple in my computer's machine.config file (along with my own DLL which was already registered there). I don't particularly like this approach though since it's dependent upon the DLL version which is subject to change at any time. Hopefully MS will just add this assembly to the next version of the .Net Framework.

<runtime>
<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
  <dependentAssembly>
    <assemblyIdentity name="System.ValueTuple" publicKeyToken="cc7b13ffcd2ddd51" />
    <bindingRedirect oldVersion="0.0.0.0-99.99.99.99" newVersion="4.0.1.0" />
    <codeBase version="4.0.1.0" href="e:\exec\System.ValueTuple.dll" />
  </dependentAssembly>
  ...
</assemblyBinding>
</runtime>

Orth

System.ValueTuple has been added to .Net Framework 4.7. – Orth

This got me close but for nuget version 4.5 I had to use the following in my windows service config <dependentAssembly> <assemblyIdentity name="System.ValueTuple" publicKeyToken="cc7b13ffcd2ddd51" culture="neutral" /> <bindingRedirect oldVersion="0.0.0.0-4.0.3.0" newVersion="4.0.3.0" /> </dependentAssembly> – Relegate

Answer 2

ok this feels completely wrong but I cut

  <dependentAssembly>
    <assemblyIdentity name="System.ValueTuple" publicKeyToken="cc7b13ffcd2ddd51" culture="neutral" />
    <bindingRedirect oldVersion="0.0.0.0-4.0.3.0" newVersion="4.0.3.0" />
  </dependentAssembly>

This out of my web.config for the main application.

I was really just seeing what happened to see if there was an underlying dependency or something, not expecting it to run. It just carried on working, all the new functions I have added in the last few days still work.

Scholium

This worked for me. Djensen's solution below was also necessary, because initially I had multiple projects with different nuget versions. I suspect what happened is that, when it first built, it noticed the mismatch and so added the bindingRedirect in the app.config. So even after fixing the nuget references in all projects to be the same, this bindingRedirect still lingered. – Confession

IMO, this is the only change you need in order to get it work. – Wail

It works for me, likely that the machine already have it, by take out that runtime stuff from web.config helps. Thanks for this. – Tornado

This worked for me, too. I'm not sure how/when this entry was added, but my version of the DLL was outside the range. – Mongrel

As far as I see current version of the System.ValueTuple assembly in the .Net Framework is 4.06.26515.6 but the latest version in the nuget package is 4.0.3.0. It means if developer wants to use the nuget package System.ValueTuple then it's required to forcibly set binding redirect from 0.0.0.0-4.99.99.99 to 4.0.3.0. – Statist

There are three versions in assemblies - only AssemblyVersion really matters . You are talking about AssemblyInformationalVersion (4.06.26515.6) which is irrelevant and for information purposes only. – Ellaelladine

Answer 3

I just had this issue myself. Not on Localhost while developing, but only on production server. In the end it turned out to be some sort of conflict between .Net Framework 4.6.1 and me having System.ValueTuple installed from Nuget in version 4.5.0.

The solution turned out to be, to downgrade the System.ValueTuple Nuget package to 4.3.0. Then it worked, like nothing had ever been an issue.

I suspect that this only happened on production server, cause of a different version of .net framework installed.

Wrongful

This worked for me. I'm using System.ValueTuple in a .NET Standard 2.0 project and was having trouble running it from .NET Core 2.0 until I downgraded to 4.3.0. – Bracci

Worked for me too - I had a class library targeting .NET Standard 1.3 which was consumed by a AspNetCore project targeting 2.0. Downgrading to 4.3.0 fixed the issue - thanks! – Gathering

Exactly what my issue was, had a library using the NuGET and the unit tests using what I had locally, installing the NuGET onto the unit test project resolved the issue. – Skiascope

Answer 4

Solved it by installing .NET Framework 4.7.2 Runtime on the machine the error occurred on. Simple and no need to add bindingRedirect or downgrading NuGet packages.

https://dotnet.microsoft.com/download/dotnet-framework/net472

Flapjack

Found a random server that only had 4.6 installed. This answer should be the starting point before all the others. – Anderlecht

Answer 5

Adding on to Robin's answer for just changing the Web.config. I was able to get away with only commenting out the binding redirect tag.

<dependentAssembly>
    <assemblyIdentity name="System.ValueTuple" publicKeyToken="cc7b13ffcd2ddd51" culture="neutral" />
    <!--<bindingRedirect oldVersion="0.0.0.0-4.0.2.0" newVersion="4.0.2.0" />-->
</dependentAssembly>

This got rid of the error for me.

Cattleya

Happened for me as well and the only way was to comment out the binding redirect. However not sure why that fixes it because the version is correct. – Northeaster

Answer 6

FWIW, I had this issue on my testing project using Moq. Someone had set the project to .NET 4.7, but I was on 4.6.2. Not wanting to move to 4.7 yet, the solution was to downgrade the version to Moq 4.7.145. The System.ValueTuple v 4.3.1 worked together with it.

Raman

Moq 4.7.145 does not depend on ValueTuple that's why the downgrade works. No idea why the latest version of Moq is causing this issue. This is how i landed here. – Manmade

Answer 7

I faced the same exception when there was a nuget package version mismatch. (In the DLL was 4.3.1 used while in the main program 4.3.0.) I have resolved the issue by upgrading the packages to the same version... Checking and unifying the package versions could hopefully help you as well.

Disable

Answer 8

I hade the same issue, i solve the probleme by changing the target framwork of the project to .Net Framwork 4.7.1.

System.ValueTuple now supports .NET Framework 4.7

Esterify

Answer 9

In my solution I found 2 different trouble maker. Either in the App.config or Web.config file:

1. Version mismatch: The version installed via NuGet did not match the version in the config file. Solution: Change the version manually in the .config file.

2. Duplicate entries: I found duplicate entries for ValueTuple. In my case one for 4.0.3.0 and another one for 4.5.0. Removing the older entry solved the issue.

In another case I managed to fix the issue by removing unneeded references and getting rid of the ValueTuple NuGet package altogether.

Tallow

When you say duplicate entries: do you mean different versions in different projects? I had that and setting them all to the same version fixed this issue for me. – Skateboard

Answer 10

In my case I think something delete this dll from project and framework folders, maybe during installing something it flied; so my project during debugging couldn't find that dll and throw that error. I installed

Install-Package System.ValueTuple -Version 4.5.0

Package and than everything worked again. Before doing further complicated solutions as described above answers may installing ValueTuple package works for you.

Christcross

Answer 11

My issue was that I was developing against 4.6.1, but releasing on 4.7.2. Luckily I don't mind which .Net framework this project was built for, so I installed 4.7.2 on my developer instance, then upgraded all the Nuget packages.

(Using SQLite on AWS EC2)

Encephalic

Answer 12

If you have AutoMapper version 8.0 or lower referenced in any of your projects, it's possibly the source of the issue. See this github issue for more information.

If I understand correctly, the issue is that .NET Framework versions below version 4.7 did not have System.ValueTuple shipped with them by default, so AutoMapper was using a NuGet package reference for the assembly since it has build targets for Framework versions below 4.7. This caused some funky Microsoft stuff.

The easiest solution is to upgrade your AutoMapper references to version 8.1.0 or newer, where they have scraped all uses of the assembly from their codebase and removed the dependency.

Diachronic

The source is the framework itself, we're all victims :) – Ailyn

Answer 13

I experienced the same error "Could not load file or assembly System.ValueTuple.dll..." on my Windows Server 2016. However, the site worked fine on my dev machine.

My solution was simple, I grabbed this dll from my dev machine and dropped it in the site's "bin" folder on the server. It worked.

Nonoccurrence

Answer 14

I hope this isn't thread necromancy, because this is still the #1 searched thing on Google. None of the other comments worked for me sadly.

We resolved this issue recently after over a year with this problem. The issue was a package called 'GitVersion'. So for anybody who is still struggling with this and looking around the forums I know quite a few are; I would advise you check your packages and see what their dependencies are.

Klemens

Answer 15

Fixed this by switching the Copy Local flag on my reference to System.ValueTuple from copy always to none. (It was on an assembly containing tests).

Hagiography

Answer 16

Right clicking References and choosing "Migrate packages.config to PackageReference..." solved the problem for me (and other similar issues).

Celluloid

Answer 17

I had this same issue with an AutoMapper 8.0.0.0 dependency on version 4.5 after upgrading from .NET 4.5.1 to 4.6.1. Reinstalling the automapper nuget package worked for me.

Oliphant

I had to downgrade AutoMapper to 6.2.2 to get it working. – Nicknickel

Answer 18

IF your are unable to update .Net Framework to the latest version, then downgrade Package: Microsoft.Net.Compilers to the version up to 2.10. This solved the issue in my case.

Burley

This seems to be a potential answer to a question, but not the question which was asked here. – Bilk

Answer 19

I had a library which used a newer version of the System.ValueTuple NuGet package. I then used another library which caused me to use the older version installed in the main project for the first time. That caused this exception to reveal itself. Updating both (or, converging them in any way - downgrading both is fine too) - fixed the issue.

Aphrodisia

Answer 20

I resolved this issue by installing System.ValueTuple from nuget. It was not previously installed but I guess RestSharp or another library is using it.

So this got it fixed.

Enchondroma

Answer 21

Solved it by installing VS 2019.

Levite

Answer 22

I had this issue in a Visual Studio setup/installer project. For some reason my project had multiple instances of System.ValueTuple.dll:

Deleting the extras at the bottom made the setup project build. For one of them I had to right click, choose "Find In Editor", and delete from the resulting window. Otherwise I got a cryptic error (something to the effect of "the parameter is incorrect" if I recall correctly).

Shortly