DomainModel.cs

public class Blog
{
    private readonly List<Post> posts = new List<Post>();

    public string Name { get; }
    public Guid Id { get; }

    public IReadOnlyCollection<Post> Posts => posts.AsReadOnly();

    private Blog()
    {
    }

    public Blog(string name)
    {
        Name = name;
        Id = Guid.NewGuid();
    }

    public void CreatePost(string title, string content)
    {
        this.posts.Add(new Post(title, content));
    }

    public void RemovePost(Guid postId)
    {
        var postToRemove = posts.FirstOrDefault(x => x.Id == postId);

        if (postToRemove != null)
        {
            posts.Remove(postToRemove);
        }
    }
}

public class Post
{
    public string Title { get; }
    public string Content { get; }
    public Guid Id { get; }

    private Post()
    {
    }

    public Post(string title, string content)
    {
        Id = Guid.NewGuid();
        Title = title;
        Content = content;
    }
}