Code Analysis ReferenceAnalyzersRCS1231On this pageRCS1231: Make parameter ref read-onlyPropertiesPropertyValueDefault Severitydisabled by defaultMinimum language version7.2ExamplesExample #1diagnostic.csreadonly struct C{ void M(C c) { }}fix.csreadonly struct C{ void M(in C c) { }}Applies toExtension for VS 2022Extension for VS CodeExtension for Open VSXPackage Roslynator.Analyzers