Example of registration and use of event bus pattern in UdonSharp for VRChat :)

MainMenu.cs

using UnityEngine;
using VRCBilliardsCE.Packages.com.vrcbilliards.vrcbce.Runtime.ScriptsV2.Core;
using VRCBilliardsCE.Packages.com.vrcbilliards.vrcbce.Runtime.ScriptsV2.Core.Infrastructure;

namespace VRCBilliardsCE.Packages.com.vrcbilliards.vrcbce.Runtime.ScriptsV2.Menu.Domain
{
    public enum State
    {
        // The main menu is closed.
        Closed,
        // The main menu is locked and cannot be used.
        Locked,
        // The main menu is in the main menu.
        InMainMenu,
        // The main menu is hidden due to being in game.
        InGame,
        // The main menu is in tutorial mode.
        InTutorial
    }
    
    public class MainMenu : LocalBehaviour
    {
        public BaseMenuImpl menu;
        public DependencyManager dependency;

        private State currentState = State.Closed;
        private EventBus bus;
        
        public void Start()
        {
            bus = dependency.Bus;

            bus.Register(Core.Domain.Event.MenuOpened, this, nameof(OnMenuOpened));
            bus.Register(Core.Domain.Event.MenuClosed, this, nameof(OnMenuClosed));
            bus.Register(Core.Domain.Event.PlayerRegistrationChanged, this, nameof(OnPlayerRegistrationChanged));
            bus.Register(Core.Domain.Event.GameOptionsChanged, this, nameof(OnGameSettingsChanged));
            bus.Register(Core.Domain.Event.GameStarted, this, nameof(OnGameStarted));
            bus.Register(Core.Domain.Event.GameOverCancelled, this, nameof(OnGameEnded));
            bus.Register(Core.Domain.Event.GameOverWon, this, nameof(OnGameEnded));
            bus.Register(Core.Domain.Event.MenuLocked, this, nameof(OnMenuLocked));
            bus.Register(Core.Domain.Event.MenuUnlocked, this, nameof(OnMenuUnlocked));
        }

        public void OpenMenu()
        {
            if (currentState != State.Closed)
            {
                Debug.Log("was not closed; discarding");
                
                return;
            }
            
            Debug.Log("raising menuopened");
            
            bus.Raise(Core.Domain.Event.MenuOpened);
        }

        public void CloseMenu()
        {
            if (currentState != State.InMainMenu)
            {
                Debug.Log("was not open; discarding");
                
                return;
            } 
            
            Debug.Log("raising menuclosed");
            
            bus.Raise(Core.Domain.Event.MenuClosed);
        }

        public void StartGame()
        {
            if (currentState != State.InMainMenu)
            {
                return;
            } 
            
            bus.Raise(Core.Domain.Event.MenuStartedGame);
        }

        public void JoinGame()
        {
            if (currentState != State.InMainMenu)
            {
                return;
            } 
        }

        public void LeaveGame()
        {
            if (currentState != State.InMainMenu)
            {
                return;
            } 
            
            bus.Raise(Core.Domain.Event.PlayerRegistrationChanged);
        }

        public void OnMenuOpened()
        {
            if (currentState != State.Closed)
            {
                return;
            }

            currentState = State.InMainMenu;
            
            menu.OpenMenu();
        }

        public void OnMenuClosed()
        {
            if (currentState != State.InMainMenu)
            {
                return;
            }

            currentState = State.Closed;
            
            menu.CloseMenu();
        }

        public void OnMenuLocked()
        {
            if (currentState == State.Locked)
            {
                return;
            }

            currentState = State.Locked;

            menu.LockMenu();
        }

        public void OnMenuUnlocked()
        {
            if (currentState != State.Locked)
            {
                return;
            }

            currentState = State.Closed;

            menu.UnlockMenu();
        }
        
        public void OnGameStarted() {}
        
        public void OnGameEnded() {}

        public void OnPlayerRegistrationChanged() {}
        
        public void OnGameSettingsChanged() {}
    }
}