Adding New APIs to an Existing WinForms Control or Component

These rules apply when adding new public or protected members — properties, methods, events, delegates, enums, or interfaces — to an existing WinForms control or component. For creating entirely new controls, or for general coding standards, see the coding-standards skill instead.

Golden rule: Every new public API must be tracked, reviewed, documented, and serialization-safe before it ships.

1. API Issue Tracking

Every new public API surface change requires a corresponding API proposal issue in the api-suggestion format, which will be reviewed by the .NET API review board.

1.1 Check for an existing issue