EventSourcingExample.cs

interface EventStream
{
	// Just a marker interface to let you know which classes are persisted.
}

class Site : EventStream
{
	private readonly HashSet<string> _registeredUsers = new HashSet<string>();

	public string Id { get; private set; }

	public User RegisterUser(string username)
	{
		if (_registeredUsers.Contains(username.ToLower()))
		{
			throw new NonUniqueUsernameException(username);
		}

		var user = new User(username);

		_registeredUsers.Add(username.ToLower());
		
		return user;
	}
}

class User : EventStream
{
	public User(string username)
	{
		Username = username;
	}

	public int Id { get; private set; }

	public string Username { get; private set; }
}

// From UI
class UsersController : Controller
{
	public ActionResult Index(int pageIndex = 1)
	{
		// Read model backed by a database, file, in-memory, etc.
		var registeredUsersView = new RegisteredUsersView();

		var users = registeredUsersView.FindAll(pageIndex);

		return View(users);
	}

	public ActionResult Create()
	{
		return View();
	}

	[HttpPost]
	public ActionResult Create(string username)
	{
		// Magic class, depends on implementation?
		var eventStore = new EventStore();

		var site = eventStore.Get<Site>("MySite");

		try
		{
			var user = site.CreateUser(username);

			eventStore.Persist(site);
			eventStore.Persist(user);

			/**
			 * TODO: Either publish the events somehow, or let the event store
			 * publish the events, or execute the "update view logic" right away
			 * when the unit of work is disposed.
			 */

			return RedirectToAction("Index");
		}
		catch (NonUniqueUsernameException)
		{
			// TODO: Add errors...
			return View();
		}
	}
}