How to encapsulate .NET Stateless state machine

Question

I have a project where there is a mostly linear workflow. I\'m attempting to use the .NET Stateless library to act as workflow engine/state machine. The number of examples out

Answer 1

There is an article by Scott Hanselman with an example and introduction to a library. Also there few examples available on their GitHub including Bug implementation example mentioned in Scott's article that encapsulates the state machine.

Below is an example of how the state can be extracted from behavior:

public class PatientRegistrationState
{
    private StateMachine stateMachine;
    private StateMachine.TriggerWithParameters registrationTrigger;

    public PatientRegistrationState(State initialState = default(State)) {
        stateMachine = new StateMachine(initialState);

        stateMachine.Configure(WorkflowState.Unregistered)
            .Permit(WorkflowTrigger.Register, WorkflowStateType.Registered);

        stateMachine.Configure(WorkflowState.Registered)
            .Permit(WorkflowTrigger.ScheduleSampling, WorkflowState.SamplingScheduled)
            .OnEntryFrom(registrationTrigger, (date) => OnPatientRegistered(date));
    }

    public WorkflowState State => stateMachine.State;
    public Action OnPatientRegistered {get; set;} = (date) => { };

    // For state changes that do not require parameters.
    public void ChangeTo(WorkflowTrigger trigger)
    {
        stateMachine.Fire(trigger);
    }

    // For state changes that require parameters.
    public void ChangeToRegistered(DateTime dateOfBirth)
    {
        stateMachine.Fire(registrationTrigger, dateOfBirth);        
    }

    // Change to other states that require parameters...
}

public class PatientRegistration
{
    private PatientRegistrationState registrationState;
    private Patient patient;

    public PatientRegistration()
    {
        registrationState = PatientRegistrationState(WorkflowState.Unregistered)
        {
            OnPatientRegistered = RegisterPatient;
        }
    }

    public Patient RegisterPatient(DateTime dateOfBirth)
    {
        registrationState.ChangeToRegistered(dateOfBirth);
        logger.Info("State changed to: " + registrationState.State);
        return patient;
    }

    private void RegisterPatient(DateTime dateOfBirth)
    {
        // Registration code
    }
}