Delete the Event Switch: Runtime Dispatch with dynamic in C#

Dynamic dispatch is achieved through runtime type-based method selection. Writing this manually involves adding code for each event type, which is prone to errors and maintenance issues. The provided C# code demonstrates a cleaner approach using dynamic casting at a single point in the code. By casting the event to dynamic at the boundary, the C# runtime binder automatically selects the appropriate handler method based on the event's runtime type.

The code defines a hierarchy of domain events as sealed records inheriting from a base BaseEvent class. A processor class, EventProcessor, handles these events by casting them to dynamic within a single handler method, HandleAsync. The method delegates the actual handling to three overloaded private methods, Dispatch, each corresponding to a specific event type. A fallback method handles any unhandled event types, throwing a NotSupportedException with a descriptive message.

The dynamic casting enables the compiler to select the most specific handler method at runtime, eliminating the need for manual switch statements and reducing maintenance overhead. While the runtimeBinderException thrown for unrecognized event types may seem confusing, the fallback handler provides a clear, user-defined error message.

Dynamic casting does not impact performance significantly, as the runtime cache the results of the dispatch for each event type. However, it is essential to ensure null checks and proper return types to avoid runtime errors. By delegating the event handling to the runtime, developers can focus on writing specific handlers for each event type, leading to cleaner, more maintainable code.