SMAPI/StardewModdingAPI/Events/Menu.cs

using System;
using StardewValley.Menus;

namespace StardewModdingAPI.Events
{
    public static class MenuEvents
    {
        public static event EventHandler<EventArgsClickableMenuChanged> MenuChanged = delegate { };

        public static void InvokeMenuChanged(IClickableMenu priorMenu, IClickableMenu newMenu)
        {
            MenuChanged.Invoke(null, new EventArgsClickableMenuChanged(priorMenu, newMenu));
        }
    }
}