Prototype

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.Serialization.Formatters.Binary;
using System.Text;
using System.Threading.Tasks;

namespace Prototype
{
    static class ExtensionMethods
    {
        public static T DeepCopy<T>(this T self)
        {
            if (!typeof(T).IsSerializable)
                throw new ArgumentException("type must be serializable");
            if (ReferenceEquals(self, null))
                return default(T);

            var formatter = new BinaryFormatter();
            using (var stream = new MemoryStream())
            {
                formatter.Serialize(stream, self);

                stream.Seek(0, SeekOrigin.Begin);
                return (T)formatter.Deserialize(stream);
            }


        }
    }

    class EmployeeFactory
    {
        private static Contact main = new Contact() { WorkAdress = new Address() { City = "London", Street = "221b Baket Sr", Suite = 100 } };
        private static Contact aux = new Contact() { WorkAdress = new Address() { City = "London", Street = "250", Suite = 100 } };

        private static Contact NewEmployee(string name, int suite, Contact prototype)
        {
            var result = prototype.DeepCopy();
            result.Name = name;
            result.WorkAdress.Suite = suite;
            return result;
        }
        public static Contact NewMainOfficeEmployee(string name, int suite)
        {
            return NewEmployee(name, suite, main);
        }
        public static Contact NewAuxOfficeEmployee(string name, int suite)
        {
            return NewEmployee(name, suite, aux);
        }
    }
    [Serializable]
    public class Contact
    {
        public string Name;
        public Address WorkAdress;

        public override string ToString()
        {
            return $"Name: {Name}, WorkAdress: {WorkAdress}";
        }
    }
    [Serializable]
    public class Address
    {
        public string Street;
        public string City;
        public int Suite;

        public override string ToString()
        {
            return $"Street: {Street}, City: {City}, Suite: {Suite}";
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            var john = EmployeeFactory.NewMainOfficeEmployee("John", 100);
            var jill = EmployeeFactory.NewAuxOfficeEmployee("Jill", 1000);
            Console.WriteLine(john);
            Console.WriteLine(jill);

            Console.ReadKey();
        }
    }
}