private async Task SetCurrentStateFromTransition(ITransition transition)
{
_ = transition ?? throw new ArgumentNullException(nameof(transition));
IState newState = await transition.GetState(this).ConfigureAwait(false) ?? throw new NullReferenceException("Transition returned NULL state.");
IState oldState = CurrentState;
CurrentState = newState;
if (oldState != null)
{
await oldState.OnExited(newState).ConfigureAwait(false);
}
await newState.OnEntered(oldState).ConfigureAwait(false);
}