Flyweight Pattern Gist

Zone.cs

    public class Zone : IEquatable<Zone> 
    	//An immutable flyweight...This represents a domain value object
    {
        public string ZipCode { get; }
	
	 public IReadOnlyCollection<string> AvailableCouriers { get; private set; }

        public Zone(string zipCode)
        {
           ZipCode = zipCode;
	    AvailableCouriers = new List<string>();
        }

        public Zone(string zipCode, IEnumerable<string> couriers) : this(zipCode)
        {
	    AvailableCouriers = new List<string>(couriers.Distinct());
        }

        public Zone RegisterCourier(string courier)
        {
	    var newCouriers = new List<string>(AvailableCouriers)
           {
               courier
           };

           return new Zone(ZipCode, newCouriers);
         }
	 
	 public bool Equals(Zone other)
	 {
	    if (other == default(Zone)) 
	    	return false;
		
	    if (ReferenceEquals(this, other)) 
	    	return true;
		
	    if (!string.Equals(ZipCode, other.ZipCode, StringComparison.OrdinalIgnoreCase)) 
	    	return false;
		
	    if (AvailableCouriers.Count != other.AvailableCouriers.Count) 
	    	return false;
		
	    if (!AvailableCouriers.All(x => other.AvailableCouriers.Contains(x))) 
	    	return false;
		
	    return true;
	  }
    }