public interface IContactSubmitter
{
	void SubmitContact(string message);
}

public class ContactController : Controller
{
	private readonly IContactSubmitter _contactSubmitter;
	public ContactController(IContactSubmitter contactSubmitter)
	{
		_contactSubmitter = contactSubmitter;
	}

	[HttpPost]
	public ViewResult Contact(string message)
	{
		// Pretend there was some validation done here..
		if (ValidateMessage(message))
			_contactSubmitter.SubmitContact(message);

		return View();
	}
}