Equality implementation in C#

EqualityDemo.cs

namespace EqualityDemo
{
    public class Person : IEquatable<Person>
    {
        public string GivenName { get; }
        public string FamilyName { get; }
        public Address Address { get; }
        
        public override bool Equals(object other)
        {
            return Equals(other as Person);
        }
        
        public override int GetHashCode()
        {
            return HashCode.Combine(GivenName, FamilyName, Address);
        }
        
        public bool Equals(Person other)
        {
            return Equals(this, other);
        }
        
        public static bool Equals(Person a, Person b)
        {
            if (ReferenceEquals(a, b))
            {
                return true;
            }
            
            // You can use a == null || b == null here, *unless* you are overriding the equality operators,
            // in which case you'll end up with a StackOverflowException
            if (ReferenceEquals(a, null) || ReferenceEquals(b, null))
            {
                return false;
            }
            
            return a.GivenName == b.GivenName &&
                   a.FamilyName == b.FamilyName &&
                   a.Address == b.Address;
        }
    }
    
    public class Address : IEquatable<Address>
    {
        public string Line1 { get; }
        public string Line2 { get; }
        public string City { get; }
        public string County { get; }
        public PostCode PostCode { get; }
        
        public override bool Equals(object other)
        {
            return Equals(other as Address);
        }
        
        public override int GetHashCode()
        {
            return HashCode.Combine(Line1, Line2, City, County, PostCode);
        }
        
        public bool Equals(Address other)
        {
            return Equals(this, other);
        }
        
        public static bool Equals(Address a, Address b)
        {
            if (ReferenceEquals(a, b))
            {
                return true;
            }
            
            if (ReferenceEquals(a, null) || ReferenceEquals(b, null))
            {
                return false;
            }
            
            return a.Line1 == b.Line1 &&
                   a.Line2 == b.Line2 &&
                   a.City == b.City &&
                   a.County == b.County &&
                   a.PostCode == b.PostCode;
        }
    }
    
    public class PostCode : IEquatable<PostCode>
    {
        private string _postcode;
        
        public PostCode(string postcode)
        {
            _postcode = postcode ?? throw new ArgumentNullException(postcode);
        }
        
        public override bool Equals(object other)
        {
            return Equals(other as PostCode);
        }
        
        public override int GetHashCode()
        {
            return _postcode.GetHashCode();
        }
        
        public override string ToString()
        {
            return _postcode;
        }
        
        public bool Equals(PostCode other)
        {
            return Equals(this, other);
        }
        
        public static bool Equals(PostCode a, PostCode b)
        {
            if (ReferenceEquals(a, b))
            {
                return true;
            }
            
            if (ReferenceEquals(a, null) || ReferenceEquals(b, null))
            {
                return false;
            }
            
            return a._postcode == b._postcode;
    }
}