C# State Patterns

The logic for each state is encapsulated into its own class. The controller uses a factory method on the enum to create a new instance of the desired state class.

CalbackStatePattern

The state object calls the controller service function directly indicating the state that it should transition to. The state and controller and tightly coupled, as the state uses a reference to the controller passed to the function. Alternatively this could be provided by dependency injection into the state constructor.

Event Aggregator Pattern

The state object publishes an event to a central event aggregator requesting a state transition. The controller subscribes to the event aggregator for state transition event requests. This extra level of abstraction reduces the knowledge the controller has about how the source of the events. A centralised aggregator class also facilitates extra features that may be required such as authentiation, recording and failure recovery mechanisms.

Raise Event Pattern

To reduce the coupling between the states and controller, the state publishes an event without knowledge of its subscribers. The state object publishes an event to its direct subscribers requesting a state transition. The controller subscribes directly to the state object for the event.

Sequential Pattern

All the state objects are provided to the controller via dependency injection using reflection to locate all objects that implement the ITestState interface. The state object calls the controller service function directly to request transition to the next ordered state. Additional states can be introduced without changing the controller or factory code.

State Manager Rule Pattern

The ConnectionService performs the role of a state manager, evaluating the transition rules for each state and performing the rule if necessary. Each state defines the rules that govern its transition to other states. On key press input, the Connection Service enumerates the rules for the current state. The states encapsulate the logic for transitions, but require access to the context specific data - in this case the key press - to make a decision as to whether to transition or not.