The most basic state machine class and state interface in C#, free of enumeration.

State.cs

	public interface State
	{
		void Enter();
		void Run();
		void Exit();
	}

	public class StateMachine
	{
		State currentState;

		public void ChangeState(State newState)
		{
			if(currentState == newState || newState == null) return;

			if(currentState != null) currentState.Exit();
			currentState = newState;
			currentState.Enter();
		}


		public void UpdateState()
		{
			if(currentState != null) currentState.Run();
		}


		public void ResetState()
		{
		    if(currentState == null) return;

			currentState.Exit();
			currentState.Enter();
		}
	}