Forum

public abstract class BaseEntity
{
    public int Id { get; set; }
}

public class Forum : BaseEntity
{
    public string Name { get; set; } // movie, cartoon, book, comics, anime, manga, other
    public string Description { get; set; }

    public virtual IEnumerable<Post> Posts { get; set; }
}

public class Post : BaseEntity
{
    public int ForumId { get; set; }

    public int AuthorId { get; set; }
    public virtual ApplicationUser Author { get; set; }

    public string Title { get; set; }
    public string Text { get; set; }
    public virtual IEnumerable<Attachment> Attachments { get; set; }

    public virtual IEnumerable<Comment> Comments { get; set; }

    public int Rating { get; set; } // haven't "-1"; can't be negative
    public bool IsSolved { get; set; }

    public DateTime Created { get; set; }
    public DateTime Updated { get; set; } // at first equal to 'Created'

    public bool Show { get; set; } // for moderate
}

public class ApplicationUser : IdentityUser<int>
{
    public string Avatar { get; set; }
    public string Cover { get; set; } // Background Image in user profile page
    public int Karma { get; set; }
}

public class Attachment : BaseEntity
{
    public AttachmentType Type { get; set; }
    public string Link { get; set; }
}

public enum AttachmentType
{
    Image,
    Video,
    Link
}

public class Comment : BaseEntity
{
    public int PostId { get; set; } // owned post id
    public int? ParentId { get; set; } // to whom the answer

    public int AuthorId { get; set; }
    public virtual ApplicationUser Author { get; set; }

    public string Text { get; set; }
    public virtual IEnumerable<Attachment> Attachments { get; set; }

    public int Rating { get; set; } //? "-1" divide by 2 when go to karma
    public bool IsCorectAnswer { get; set; }

    public DateTime Created { get; set; }
    public DateTime Updated { get; set; } // at first equal to 'Created'

    public bool Show { get; set; } // for moderate
}