hn-dotnet/Domain/Link.cs

using System;

namespace HN.Domain
{
  public sealed class Link : Votable
  {
    public Guid Id { get; }
    public string Url { get; }
    public DateTime CreatedAt { get; }
    public Guid CreatedBy { get; }

    private Link(Guid createdBy, string url) : base()
    {
      Id = Guid.NewGuid();
      CreatedBy = createdBy;
      CreatedAt = DateTime.UtcNow;
      Url = url;
    }

    public static Link FromUrl(Guid posterId, string url)
    {
      return new Link(posterId, url);
    }

    public Comment AddComment(Guid userId, string content)
    {
      return new Comment(Id, userId, content);
    }
  }
}