Could not find a part of the path ... bin\roslyn\csc.exe

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I am trying to run an ASP.NET MVC (model-view-controller) project retrieved from TFS (Team Foundation Server) 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.

After few days of research, I understood that Roslyn is a .NET compiler platform that offers advanced 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 did I intend to use Roslyn in my project.

Segno answered 25/9, 2015 at 10:36 Comment(0)

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The problem with the default VS2015 templates is that the compiler isn't actually copied to the tfr\bin\roslyn\ directory, but rather the {outdir}\roslyn\ directory

Add this code in your .csproj file:

<Target Name="CopyRoslynFiles" AfterTargets="AfterBuild" Condition="!$(Disable_CopyWebApplication) And '$(OutDir)' != '$(OutputPath)'">
    <ItemGroup>
      <RoslynFiles Include="$(CscToolPath)\*" />
    </ItemGroup>
    <MakeDir Directories="$(WebProjectOutputDir)\bin\roslyn" />
    <Copy SourceFiles="@(RoslynFiles)" DestinationFolder="$(WebProjectOutputDir)\bin\roslyn" SkipUnchangedFiles="true" Retries="$(CopyRetryCount)" RetryDelayMilliseconds="$(CopyRetryDelayMilliseconds)" />
</Target>

Coca answered 25/9, 2015 at 10:44 Comment(15)

This does not resolve my issue. Now I get 'Could not find file 'C:\B8akWorkspace\B8akProject\B8akSolution\B8AK.Portal\bin\roslyn\csc.exe'. Please notice that when I create a new MVC project in VS2015 I don't see the mentioned configuration in .csproj and it runs perfectly fine in the browser – Segno 25/9, 2015 at 10:59

Thanks. I am now able to build and run the project in the browser after I downloaded the Roslyn directory and placing it in the /bin folder. I did not put the PstBuildEvent mentioned above and it still works. Maybe you want to edit your answer above and mention the need to manully placing the Roslyn files and to better reflect the solution. – Segno 25/9, 2015 at 14:20

Well, in a normal situation; you should have the compiler inside your $(OutDir)roslyn*.* folder, so this script will copy the compiler to the binfolder of your project. Apparently your installation of vs2015 did not include the compiler. – Coca 25/9, 2015 at 15:9

Hmm... Wouldn't the "start /min" mean that xcopy is running in a separate process while your build process continues merrily on its way creating a potential race condition? – Aciculate 15/12, 2015 at 16:20

Actually it is not a matter of VS. The compiler comes from a NuGet package - see my answer below. Adding the compiler binaries manually to the project is not the right solution I think. – Tittle 10/2, 2016 at 13:12

This should work without modifying the proj files. that's just fixing the symptom. doing a full rebuild should result in those files being there. – Luxate 14/9, 2017 at 11:4

@Segno Update MS dos.compiler in Nuget as well – Frodine 8/1, 2018 at 4:59

I've used this to deploy in the AppHarbor also. Just make sure to include csc.exe and all *.dll in the packages folder of Microsoft.Net.Compilers package. I am using VS 2017 CE, ASP .NET MVC 5 targeting .NET 4.5.2 Framework just for reference. – Seamark 10/2, 2018 at 14:48

I found updating Microsoft.CodeDom.Providers.DotNetCompilerPlatform to 1.0.8 and Microsoft.Net.Compilers 2.6.1 helped me a lot. I didnt need to add this extra target. Looks like something similar was added in a later version of the tooling: github.com/aspnet/RoslynCodeDomProvider/commit/… – Epicene 13/2, 2018 at 16:1

I dont know but adding this target does not copy roslyn folder. I am using VS 2017. – Kattiekatuscha 15/3, 2018 at 5:59

I have updated the version of Microsoft.Net.Compilers to version 2.10.0 from the Nuget and it has been the solution for me. I'm using targetFramework="4.6.2" – Manatee 16/11, 2018 at 12:39

suggest deleting obj and bin folder first before experimenting on newer the new ides. – Emotive 29/3, 2019 at 23:55

Don't add code to your solution just because VisualStudio is not behaving! Look at the other answers below. – Egocentrism 19/9, 2019 at 14:39

hmm.. similar to this issue -- Nugets fix it – Pyrrhonism 23/1, 2020 at 6:4

Solved for me after removing <system.codedom> from web.config – Horsley 30/3, 2021 at 5:5

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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.

Tittle answered 21/12, 2015 at 8:23 Comment(1)

For some reason, I had to go into the Nuget Package Manager and manually select the latest version (3.6.0) for this to work, if anyone still faces the error after running the command above. – Tonkin 9/3, 2022 at 19:22

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594

The problem with the default VS2015 templates is that the compiler isn't actually copied to the tfr\bin\roslyn\ directory, but rather the {outdir}\roslyn\ directory

Add this code in your .csproj file:

<Target Name="CopyRoslynFiles" AfterTargets="AfterBuild" Condition="!$(Disable_CopyWebApplication) And '$(OutDir)' != '$(OutputPath)'">
    <ItemGroup>
      <RoslynFiles Include="$(CscToolPath)\*" />
    </ItemGroup>
    <MakeDir Directories="$(WebProjectOutputDir)\bin\roslyn" />
    <Copy SourceFiles="@(RoslynFiles)" DestinationFolder="$(WebProjectOutputDir)\bin\roslyn" SkipUnchangedFiles="true" Retries="$(CopyRetryCount)" RetryDelayMilliseconds="$(CopyRetryDelayMilliseconds)" />
</Target>