Primitives Considered Evil

gistfile1.cs

using System;

namespace ThePast
{
	public class User
	{
		public string FirstName { get; set; }
		public string LastName { get; set; }
		public string EmailAddress { get; set; }
		
		public User(string firstName, string lastName, string emailAddress)
		{
			FirstName = firstName;
			LastName = lastName;
			EmailAddress = EmailAddress;
		}
	}
}

namespace TheFuture
{
	public class MainClass
	{
		public static void Main (string[] args)
		{
			var user = new User(new FirstName("Ian"), new LastName("Joyce"), new EmailAddress("ian.joyce@gmail.com"));
			Console.WriteLine(user);
			
			// Change my name and email.
			var user2  = user.With(new EmailAddress("ian.joyce2@gmail.com")).With(new LastName("Joyce 2"));
			Console.WriteLine(user2);
			
			Console.ReadKey();
		}
	}

	// Implementing some ideas from http://jessitron.blogspot.com/2012/03/strong-typing-in-java-religious.html in C#
	// Favor types and immutability.
	
	public class User
	{
		private readonly FirstName firstName;
		public FirstName FirstName { get { return firstName; } }
		
		private readonly LastName lastName;
		public LastName LastName { get { return lastName; } }
		
		private readonly EmailAddress emailAddress;
		public EmailAddress EmailAddress { get { return emailAddress; } }
		
		public User(FirstName firstName, LastName lastName, EmailAddress emailAddress)
		{
			this.firstName = firstName;
			this.lastName = lastName;
			this.emailAddress = emailAddress;
		}
		
		public User With(FirstName firstName)
		{
			return new User(firstName, LastName, EmailAddress);	
		}
		
		public User With(LastName lastName)
		{
			return new User(FirstName, lastName, EmailAddress);
		}
		
		public User With(EmailAddress emailAddress)
		{
			return new User(FirstName, LastName, emailAddress);
		}
		
		public override string ToString()
		{
			return string.Format("{0} {1} ({2})", FirstName, LastName, EmailAddress);
		}
	}
	
	// These should override Equals and HashCode.
	
	public class FirstName
	{
		private readonly string @value;
		public string Value { get { return value; } }
		
		public FirstName(string @value)
		{
			this.value = @value;
		}
		
		public override string ToString()
		{
			return Value;
		}
	}
	
	public class LastName
	{
		private readonly string @value;
		public string Value { get { return value; } }
		
		public LastName(string @value)
		{
			this.value = @value;
		}			
		
		public override string ToString()
		{
			return Value;
		}
	}
	
	public class EmailAddress
	{
		private readonly string @value;
		public string Value { get { return value; } }
		
		public EmailAddress(string @value)
		{
			this.value = @value;
		}
		
		public override string ToString()
		{
			return Value;
		}
	}
}