Answer by Adam Smith for Could not find a part of the path ... bin\roslyn\csc.exe

I have multiple .NET Framework 4.8 ASP.Net web apps in the same solution. They are still using packages.config and are using Microsoft.CodeDom.Providers.DotNetCompilerPlatform version 4.1.0.

Consistently and reproducibly I get this problem of the roslyn folder not being created in the bin folder when building in Visual Studio 2022. To reproduce:

1. Close Visual Studio 2022
2. Delete the packages folder and all the obj and bin folders
3. Open Visual Studio 2022
4. Restore Nuget packages for the solution (confirm that Microsoft.CodeDom.Providers.DotNetCompilerPlatform exists in packages folder).
5. Build solution.

Every single time the bin folders of the web apps do not contain the roslyn folder. I have to do multiple cleans and builds and/or rebuilds and eventually the roslyn folder shows up and the web apps work. I haven't been able to identify a pattern as to when a build will finally copy the roslyn folder.

Solution

I have updated the .csproj files of the web apps to include

<PropertyGroup><RoslynCopyToOutDir Condition="$(RoslynCopyToOutDir) == ''">true</RoslynCopyToOutDir><RoslynToolPath Condition="'$(RoslynToolPath)' == ''">..\packages\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.4.1.0\tools\Roslyn-4.1.0</RoslynToolPath></PropertyGroup>

Now following the same reproduction steps above the roslyn folder is copied to the bin folder the very first time the solution is built.

I copied this from the Microsoft.CodeDom.Providers.DotNetCompilerPlatform.targets file located in \packages\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.4.1.0\build\net472.

Since this now works consistently I am assuming something is going wrong with the import of the targets configured in the .csproj files. They do contain the below import statement, so I am not sure what is interfering with the imports intermittently.

<Target Name="EnsureNuGetPackageBuildImports" BeforeTargets="PrepareForBuild"><PropertyGroup><ErrorText>This project references NuGet package(s) that are missing on this computer. Use NuGet Package Restore to download them.  For more information, see http://go.microsoft.com/fwlink/?LinkID=322105. The missing file is {0}.</ErrorText></PropertyGroup><Error Condition="!Exists('..\packages\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.4.1.0\build\net472\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.targets')" Text="$([System.String]::Format('$(ErrorText)', '..\packages\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.4.1.0\build\net472\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.targets'))" /></Target><Import Project="..\packages\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.4.1.0\build\net472\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.targets" Condition="Exists('..\packages\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.4.1.0\build\net472\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.targets')" />