Could not load file or assembly 'System.Runtime.CompilerServices.Unsafe, Version=4.0.4.1, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies.

Question

Can someone tell me why the following powershell code no longer works with newer MSBuild 17 (It works fine with MSBuild 15)

$retVal = Add-Type -Path "C:\Program Files\Microsoft Visual Studio\2022\Enterprise\MSBuild\Current\Bin\Microsoft.Build.dll" #load DLL

$ProjectCollection = [Microsoft.Build.Evaluation.ProjectCollection]::GlobalProjectCollection;

$ProjectCollection.UnloadAllProjects();

I always get the following error

Could not load file or assembly 'System.Runtime.CompilerServices.Unsafe, Version=4.0.4.1, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.

Why does MSBuild 17 want to use such an OLD version 4.0.4.1? This version is not installed anywhere.

Why would it need to be for new MSBuild?

Answer 1

Hello @flagrant99 ,

Welcome to Microsoft Q&A forum.

The error message does mention that "could not load file or assembly … The system cannot find the file specified". If you try to install the System.Runtime.CompilerServices.Unsafe.dll assembly(version 4.5.3 corresponding to assembly version 4.0.4.1, you can run ildasm in Developer Command Prompt for Visual Studio and use ildasm tool to check the assembly version of the dll file) and register it into GAC, the error should disappear.

Please try to download the Nuget package from here: System.Runtime.CompilerServices.Unsafe. After downloading, you will get a .nupkg file, move it to a clean folder. Rename the file extension to .zip, open it, open the lib folder, open the net461 folder and you should see the dll file, copy the folder path, let’s say the path is C:\XXXX\XXXX.

Run Developer Command Prompt for Visual Studio as administrator, and run following commands:

cd C:\XXXX\XXXX

gacutil /i System.Runtime.CompilerServices.Unsafe.dll

Sincerely,

Tianyu

---

If the answer is the right solution, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Answer 2

That error (with varying version numbers) has been encountered several times. You might start here: https://github.com/dotnet/msbuild/issues/5192

It would probably also be a good idea to add one of the "Visual Studio" tags to your question.

I don't think the problem is with PowerShell, though.

Answer 3

It runs fine from Powershell 7.3.4.

I guess Powershell 5.1 does not work with newer MSBuild.

I think the problem is the GAC. The GAC breaks things. Powershell 7.x does not load from the GAC at all and it works fine.

See here:

https://learn.microsoft.com/en-us/powershell/scripting/dev-cross-plat/resolving-dependency-conflicts?view=powershell-7.3

Answer 4

Hi,

I tried your solution but it doesn't work when building native image. Is there any way to fix this?