C# – Could not find a part of the path … bin\roslyn\csc.exe

.netasp.netasp.net-mvcc++roslyn

I am trying to run Asp.net MVC project retrieved from TFS source control. I have added all assembly references and I am able to build and compile successfully without any error or warning.

But I get the following error in the browser:

Could not find a part of the path
'C:\B8akWorkspace\B8akProject\B8akSolution\B8AK.Portal\bin\roslyn\csc.exe'.

Here is a full screenshot of the error page.

enter image description here

After few days of research, I understood that Roslyn is .Net compiler platform that offers advance compiling features. However, I do not understand why my build is trying to find \bin\roslyn\csc.exe because I did not configure anything related to Roslyn nor I intend to use Roslyn in my project.

Best Solution

TL; DR

run this in the Package Manager Console:

Update-Package Microsoft.CodeDom.Providers.DotNetCompilerPlatform -r

More information

This problem is not related to Visual Studio itself, so answers suggesting adding build steps to copy files over are rather a workaround. Same with adding compiler binaries manually to the project.

The Roslyn compiler comes from a NuGet package and there is/was a bug in some versions of that package (I don't know exactly which ones). The solution is to reinstall/upgrade that package to a bug-free version. Originally before I wrote the answer back in 2015 I fixed it by installing following packages at specific versions:

  • Microsoft.Net.Compilers 1.1.1
  • Microsoft.CodeDom.Providers.DotNetCompilerPlatform 1.0.1

Then I looked into .csproj and made sure that the paths to packages are correct (in my case ..\..\packages\*.*) inside tags <ImportProject> on top and in <Target> with name "EnsureNuGetPackageBuildImports" on the bottom. This is on MVC 5 and .NET Framework 4.5.2.