Event Sourcing

using System;
using System.Linq;
using System.Collections.Generic;

namespace EventSourcing
{
	public abstract class EventBase
	{
		public int Id { get; }
		public EventBase(int entityId)
		{
			Id = entityId;
		}

		public abstract void Affect(User entity);
	}

	public class User
	{
		public int Id { get; private set; }
		public string Name { get; private set; }
		public override string ToString()
		{
			return $"User = {Id} - {Name}";
		}

		internal User() { }
		public User(int id, string name)
		{
			Apply(new UserCreatedEvent(id, name));
		}

		public void SetName(string name)
		{
			Apply(new UserNameChangedEvent(this.Id, name));
		}

		public void Apply(UserCreatedEvent userCreatedEvent)
		{
			this.Id = userCreatedEvent.Id;
			this.Name = userCreatedEvent.Name;

			events.Add(userCreatedEvent);
		}
		public void Apply(UserNameChangedEvent userNameChangedEvent)
		{
			this.Name = userNameChangedEvent.Name;

			events.Add(userNameChangedEvent);
		}


		private ICollection<EventBase> events = new List<EventBase>();
		public IEnumerable<EventBase> Events => events;
		public void ClearEvents()
		{
			this.events.Clear();
		}
	}

	public class UserCreatedEvent : EventBase
	{
		public int Id { get; }
		public string Name { get; }

		public UserCreatedEvent(int id, string name)
			: base(id)
		{
			this.Id = id;
			this.Name = name;
		}

		public override void Affect(User entity)
		{
			entity.Apply(this);
		}
	}
	public class UserNameChangedEvent : EventBase
	{
		public string Name { get; }

		public UserNameChangedEvent(int id, string name)
			: base(id)
		{
			this.Name = name;
		}

		public override void Affect(User entity)
		{
			entity.Apply(this);
		}
	}

	public class Store
	{
		private readonly ICollection<EventBase> events = new List<EventBase>();

		public void Add(User user)
		{
			foreach (var domainEvent in user.Events)
			{
				events.Add(domainEvent);
			}
		}

		public User GetById(int id)
		{
			var domainEvents = events.Where(e => e.Id == id);

			var user = new User();
			foreach (var domainEvent in domainEvents)
			{
				domainEvent.Affect(user);
			}
			user.ClearEvents();
			return user;
		}
	}

	class Program
	{
		static void Main(string[] args)
		{
			var store = new Store();

			var user = new User(id: 1, name: "John");
			user.SetName("Jane");

			store.Add(user);

			var userFromStore = store.GetById(1);

			Console.WriteLine(userFromStore);
		}
	}
}