Liskov - step 1

ContactInformationAuctionMessageBuilder.cs

class ContactInformationAuctionMessageBuilder : IMailMessageBuilder<ContactInformationAuction>
{
	private MailMessage mailMessage;
	private StringBuilder body = new StringBuilder();

	public ContactInformationAuctionMessageBuilder()
	{
		mailMessage = new MailMessage();
	}

	public IMailMessageBuilder<ContactInformationAuction> WithTo(string to)
	{
		mailMessage.To.Add(to);
		return this;
	}

	public IMailMessageBuilder<ContactInformationAuction> WithSubject(string subject)
	{
		mailMessage.Subject = subject;
		return this;
	}

	public IMailMessageBuilder<ContactInformationAuction> WithFrom(string from)
	{
		mailMessage.From = new MailAddress(from);
		return this;
	}

	public MailMessage BuildMessage()
	{
		mailMessage.Body = body.ToString();
		return mailMessage;
	}

	public IMailMessageBuilder<ContactInformationAuction> WithEntity(ContactInformationAuction contact)
	{
		AddBodyLine("Nombre: {0}", contact.FirstName);
		AddBodyLine("Apellido: {0}", contact.LastName);
		AddBodyLine("Autor: {0}", contact.Author);
		AddBodyLine("Dimensiones: {0}", contact.Dimensions);
		return this;
	}

	private void AddBodyLine(String line, params object[] args)
	{
		body.AppendLine(String.Format(line, args));
	}
}

ContactInformationMessageBuilder.cs

public class ContactInformationMessageBuilder : IMailMessageBuilder<ContactInformation>
{
	private MailMessage mailMessage;
	private StringBuilder body = new StringBuilder();

	public ContactInformationMessageBuilder()
	{
		mailMessage = new MailMessage();
	}

	public IMailMessageBuilder<ContactInformation> WithTo(string to)
	{
		mailMessage.To.Add(to); 
		return this;
	}

	public IMailMessageBuilder<ContactInformation> WithSubject(string subject)
	{
		mailMessage.Subject = subject;
		return this;
	}

	public IMailMessageBuilder<ContactInformation> WithFrom(string from)
	{
		mailMessage.From = new MailAddress(from);
		return this;
	}

	public MailMessage BuildMessage()
	{
		mailMessage.Body = body.ToString();
		return mailMessage;
	}

	public IMailMessageBuilder<ContactInformation> WithEntity(ContactInformation contact)
	{
		AddBodyLine("Nombre: {0}", contact.FirstName);
		AddBodyLine("Apellido: {0}", contact.LastName);
		return this;
	}

	private void AddBodyLine(String line, params object[] args)
	{
		body.AppendLine(String.Format(line, args));
	}

}

ContactInformationSubsidiaryMessageBuilder.cs

class ContactInformationSubsidiaryMessageBuilder : IMailMessageBuilder<ContactInformationSubsidiary>
{
	private MailMessage mailMessage;
	private StringBuilder body = new StringBuilder();

	public ContactInformationSubsidiaryMessageBuilder()
	{
		mailMessage = new MailMessage();
	}

	public IMailMessageBuilder<ContactInformationSubsidiary> WithTo(string to)
	{
		mailMessage.To.Add(to);
		return this;
	}

	public IMailMessageBuilder<ContactInformationSubsidiary> WithSubject(string subject)
	{
		mailMessage.Subject = subject;
		return this;
	}

	public IMailMessageBuilder<ContactInformationSubsidiary> WithFrom(string from)
	{
		mailMessage.From = new MailAddress(from);
		return this;
	}

	public MailMessage BuildMessage()
	{
		mailMessage.Body = body.ToString();
		return mailMessage;
	}

	public IMailMessageBuilder<ContactInformationSubsidiary> WithEntity(ContactInformationSubsidiary contact)
	{
		AddBodyLine("Nombre: {0}", contact.FirstName);
		AddBodyLine("Apellido: {0}", contact.LastName);
		AddBodyLine("Sucursal: {0}", contact.Subsidiary);
		return this;
	}

	private void AddBodyLine(String line, params object[] args)
	{
		body.AppendLine(String.Format(line, args));
	}
}

MailBuilderTest.cs

[TestFixture]
class MailBuilderTest
{
	[Test]
	public void TestContactInformation()
	{
		// arrange
		ContactInformation contactInformation = new ContactInformation()
		{
			FirstName = "Homero",
			LastName = "Simpson"
		};

		IMailMessageBuilder<ContactInformation> mailBuilder = new ContactInformationMessageBuilder();

		// act
		MailMessage message = mailBuilder
								.WithFrom("cliente@gmail.com")
								.WithTo("empresa@gmail.com")
								.WithSubject("Hola")
								.WithEntity(contactInformation).BuildMessage();

		// assert
		Assert.That(message.From.Address, Is.EqualTo("cliente@gmail.com"));
		Assert.That(message.To, Has.All.Matches<MailAddress>(x => x.Address == "empresa@gmail.com"));
		Assert.That(message.Subject, Is.EqualTo("Hola"));
		Assert.That(message.Body, Is.StringContaining("Nombre: Homero"));
		Assert.That(message.Body, Is.StringContaining("Apellido: Simpson"));
	}

	[Test]
	public void TestContactInformationSubsidiary()
	{
		// arrange
		ContactInformationSubsidiary contactInformation = new ContactInformationSubsidiary()
		{
			FirstName = "Homero",
			LastName = "Simpson",
			Subsidiary = "Retiro"
		};

		IMailMessageBuilder<ContactInformationSubsidiary> mailBuilder = new ContactInformationSubsidiaryMessageBuilder();

		// act
		MailMessage message = mailBuilder
								.WithFrom("cliente@gmail.com")
								.WithTo("empresa@gmail.com")
								.WithSubject("Hola")
								.WithEntity(contactInformation).BuildMessage();

		// assert
		Assert.That(message.From.Address, Is.EqualTo("cliente@gmail.com"));
		Assert.That(message.To, Has.All.Matches<MailAddress>(x => x.Address == "empresa@gmail.com"));
		Assert.That(message.Subject, Is.EqualTo("Hola"));
		Assert.That(message.Body, Is.StringContaining("Nombre: Homero"));
		Assert.That(message.Body, Is.StringContaining("Apellido: Simpson"));
		Assert.That(message.Body, Is.StringContaining("Sucursal: Retiro"));
	}

	[Test]
	public void TestContactInformationAuction()
	{
		// arrange
		ContactInformationAuction contactInformation = new ContactInformationAuction()
		{
			FirstName = "Homero",
			LastName = "Simpson",
			Author = "Picasso",
			Dimensions = "3x3"
		};

		IMailMessageBuilder<ContactInformationAuction> mailBuilder = new ContactInformationAuctionMessageBuilder();

		// act
		MailMessage message = mailBuilder
								.WithFrom("cliente@gmail.com")
								.WithTo("empresa@gmail.com")
								.WithSubject("Hola")
								.WithEntity(contactInformation).BuildMessage();

		// assert
		Assert.That(message.From.Address, Is.EqualTo("cliente@gmail.com"));
		Assert.That(message.To, Has.All.Matches<MailAddress>(x => x.Address == "empresa@gmail.com"));
		Assert.That(message.Subject, Is.EqualTo("Hola"));
		Assert.That(message.Body, Is.StringContaining("Nombre: Homero"));
		Assert.That(message.Body, Is.StringContaining("Apellido: Simpson"));
		Assert.That(message.Body, Is.StringContaining("Autor: Picasso"));
		Assert.That(message.Body, Is.StringContaining("Dimensiones: 3x3"));
	}

}