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

Solution 1:

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.

Solution 2:

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>

Solution 3:

A clean and rebuild worked for me!

Solution 4:

Your build is trying to find \bin\roslyn\csc.exe because the following packages have been added to your project. Just review your packages.config file, you can have both of them there

Microsoft.CodeDom.Providers.DotNetCompilerPlatform
Microsoft.Net.Compilers

What is Roslyn and Who added them(packages) in the project : If you’re using .net Framework 4.5.2 to create projects using VS2015, you might have noticed that the project templates use Roslyn by default. Actually, Roslyn is one of open-source compilers for .NET languages from Microsoft.

Why should we delete Roslyn : If your project has Roslyn references and you are interested to deploy it on server, you will get unwanted errors on the website as many hosting providers still have not upgraded their servers and hence do not support Roslyn. To resolve this issue, you will need to remove the Roslyn compiler from the project template.

if you are not interested in using Roslyn, follow steps bellow to delete it

1. Remove NuGet packages, use the following commands from Nuget Package Console

PM> Uninstall-package Microsoft.CodeDom.Providers.DotNetCompilerPlatform
PM> Uninstall-package Microsoft.Net.Compilers

2. After you do this, your web.config file should be auto-updated. In case it is not, look for the below code in web.config file and if it is found, delete this piece of code.

<system.codedom>
    <compilers>
      <compiler language="c#;cs;csharp" extension=".cs" type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.CSharpCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" warningLevel="4" compilerOptions="/langversion:6 /nowarn:1659;1699;1701"></compiler>
      <compiler language="vb;vbs;visualbasic;vbscript" extension=".vb" type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.VBCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" warningLevel="4" compilerOptions="/langversion:14 /nowarn:41008 /define:_MYTYPE=\&quot;Web\&quot; /optionInfer+"></compiler>
    </compilers>
</system.codedom>

Solution 5:

Here is a more MSBuild way of doing this.

<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>

But I notice that the roslyn files are also in my bin directory (not in a folder). The app seems to work, though.