C# 11 is the next version of C# coming in .NET 7, and it is introducing a warning wave that issues a warning when a type is declared with all lower-case letters. This is being done so that in the future the language can begin moving away from conditional keywords and instead use full on keywords instead. The warning is alerting customers to types that may become keywords in future versions. 

Enabling High-Quality Code in .NET 

C# 11 Features Now Previewing in Visual Studio: Generic Attributes and More 

With these tools, the .NET SDK installed, and the dotnet CLI discoverable from the environment PATH, developers would have good support when developing against the newer SDK-style projects. 

Performance benefits of sealed class in .NET 

New Video: An Early Look at C# 11 

What’s the maximum number of arguments for method in C# and in .NET? 

{
  "RoslynExtensionsOptions": {
    "documentAnalysisTimeoutMs": 10000,
    "enableDecompilationSupport": true,
    "enableImportCompletion": true,
    "enableAnalyzersSupport": true,
    "diagnosticWorkersThreadCount": 8,
    "locationPaths": [
       "//path_to/code_actions.dll"
    ]
  }
}

Early peek at C# 11 features - .NET Blog