LocationTesting.cs

using Stateless;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Xml;
using System.Xml.Serialization;

namespace StatelessTest
{
    [Serializable]
    public class Location
    {

        [NonSerialized]
        private readonly System.Timers.Timer _occupancyTimer;

        private Location()
        {
            // parameterless constructor for serialization
        }

        private TimeSpan _occupancyTimeout;

        [XmlIgnore]
        public TimeSpan OccupancyTimeout
        {
            get => this._occupancyTimeout;
            set => this._occupancyTimeout = value;
        }

        [Browsable(false), EditorBrowsable(EditorBrowsableState.Never)]
        [XmlElement(DataType = "duration", ElementName = "OccupancyTimeout")]
        public string OccupancyTimeoutString
        {
            get => XmlConvert.ToString(this.OccupancyTimeout);
            set => this.OccupancyTimeout = string.IsNullOrEmpty(value) ? TimeSpan.Zero : XmlConvert.ToTimeSpan(value);
        }

        public Location Parent { get; }

        public string Name { get; set; }

        public List<Location> Children { get; set; }

        public bool IsTimerRunning { get; set; }

        public State OccupancyState
        {
            get => _state;
            set => _state = value;
        }

        public Location(Location parent)
        {
            Parent = parent;
            Children = new List<Location>();
            OccupancyTimeout = new TimeSpan(0, 0, 0, 5);
            parent?.Children.Add(this);
            _occupancyTimer = new System.Timers.Timer();
        }

        public IEnumerable<Location> AllChildren => Children.Union(Children.SelectMany(child => child.AllChildren));

        public bool HasOccupiedChildren => AllChildren.Any(child => child.OccupancyState == State.Occupied);
    }
}
// threw this in here to:
[Serializable]
public enum State
{
    UnOccupied,
    Occupied
}

// and to create:

var locations = new List<Location>();
locations.Add(new Location(null) { Name = "Home" });

locations.Add(new Location(locations.Find(x => x.Name == "Home")) { Name = "House" });
locations.Add(new Location(locations.Find(x => x.Name == "Home")) { Name = "Garden" });
locations.Add(new Location(locations.Find(x => x.Name == "Home")) { Name = "House" });
locations.Add(new Location(locations.Find(x => x.Name == "House")) { Name = "Upstairs" });
locations.Add(new Location(locations.Find(x => x.Name == "House")) { Name = "Downstairs" });