This is a cheatsheet for generating underscore for readonly field by editorconfig:
[*.{cs,vb}]
dotnet_naming_rule.private_members_with_underscore.symbols = private_fields
dotnet_naming_rule.private_members_with_underscore.style = prefix_underscore
dotnet_naming_rule.private_members_with_underscore.severity = suggestion
dotnet_naming_symbols.private_fields.applicable_kinds = field
dotnet_naming_symbols.private_fields.applicable_accessibilities = private
dotnet_naming_style.prefix_underscore.capitalization = camel_case
dotnet_naming_style.prefix_underscore.required_prefix = _