DuckDB.ExtensionKit: Building DuckDB Extensions in C#

DuckDB.ExtensionKit is an open-source toolkit that enables C# developers to build native DuckDB extensions using familiar .NET APIs. It wraps DuckDB's stable C Extension API with type-safe C# abstractions, uses a source generator to emit boilerplate (including the native entrypoint), and compiles the result via .NET Native AOT to produce a platform-native binary with no managed runtime dependency. Developers can define scalar and table functions in C# and leverage existing NuGet packages, as demonstrated with a JWT parsing extension. The project is experimental and MIT-licensed on GitHub.