CustomerId.cs

using System;

namespace Shared
{
    public class CustomerId : IEquatable<CustomerId>
    {
        public readonly string Id;

        public CustomerId(string id)
        {
            Id = id;
        }

        public bool Equals(CustomerId other)
        {
            if (ReferenceEquals(null, other)) return false;
            if (ReferenceEquals(this, other)) return true;
            return string.Equals(Id, other.Id);
        }

        public override bool Equals(object obj)
        {
            if (ReferenceEquals(null, obj)) return false;
            if (ReferenceEquals(this, obj)) return true;
            if (obj.GetType() != this.GetType()) return false;
            return Equals((CustomerId)obj);
        }

        public override int GetHashCode()
        {
            return (Id != null ? Id.GetHashCode() : 0);
        }
    }
}