Capsule is a .NET library and C# source generator that provides thread-safe object encapsulation in an automatic and boilerplate-free way.

It turns ordinary objects into thread-safe capsules. A capsule can be used concurrently without the risk of race conditions. The original interface is retained, so this is transparent for callers.

To create a capsule, you provide an implementation (green) and specify how the methods and properties (yellow) are to be encapsulated. Capsule then adds synchronization infrastructure (blue) and the hull (red), a generated interface adapter.

Apart from a few attributes and the requirement to make methods async, implementations remain free of synchronization code. This keeps code readable and focused. It also improves testability because synchronization concerns are separated.

See docs for more information.