Introduction

Capsule is a .NET library and C# source generator that provides thread-safe object encapsulation in an automatic and boilerplate-free way. It can be used as run-to-completion runtime for state machines, as actor library or just to avoid manual locking and synchronization code.

Capsule 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.