✅ How come this gives me no warning in Rider?

var f = File.Open("FDJLK", FileMode.Append);

var f = File.Open("FDJLK", FileMode.Append);

For context, I have this in MSBuild

        <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
        <AnalysisLevel>preview</AnalysisLevel>

        <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
        <AnalysisLevel>preview</AnalysisLevel>

And this in .editorconfig

dotnet_diagnostic.CA1001.severity = error
dotnet_diagnostic.CA1816.severity = error

dotnet_diagnostic.CA1001.severity = error
dotnet_diagnostic.CA1816.severity = error

What else do I have to do to make it work?