This problem usually happens when you're working on a solution with multiple projects that were created using different versions of the .NET SDK.

You may encounter this error when running dotnet build or maybe only on dotnet publish. In any case, the best way to get rid of this problem for good is the following:

  1. On the folder where your .sln file resides, create a new file named Directory.Build.props. If you're not working with a solution (not using Visual Studio), you can use create it on the root directory of your repository (usually where .gitignore is;
  2. With a text editor, add the following content to it:
<Project>
  <PropertyGroup>
    <TargetLatestRuntimePatch>true</TargetLatestRuntimePatch>
    <GenerateFullPaths>true</GenerateFullPaths>
    <LangVersion>latest</LangVersion>
  </PropertyGroup>
</Project>

What these properties do is make your projects always restore and compile using the latest version available.

Try running the command again. If all went right, it should be compiling successfully now!

  • In case it doesn't work for you, you can add these lines manually on each of the .csproj files.

I hope that helps you, thanks for reading!