This is an analyzer and codefixer for Russian letter C in English word and vice versa.
An appropriate nuget can be found here
Insert to your Directory.Build.props
the following:
<PropertyGroup>
<WarningsAsErrors>RussianC;EnglishC</WarningsAsErrors>
</PropertyGroup>
...
<!-- анализатор некорректного использования букв C/С -->
<ItemGroup Condition="'$(MSBuildProjectExtension)'=='.csproj'">
<PackageReference Include="FixRussianCAnalyzer" Version="0.2.0">
<PrivateAssets>all</PrivateAssets>
<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
</PackageReference>
</ItemGroup>
If you need to disable this analyzer in concrete file\lines you may add #pragma warning disable RussianC
or #pragma warning disable EnglishC
to the appropriate place.