VkNet c# how to implement getting multiple images from the 1st post?

Question

API

var posts = _api.Wall.Get(new WallGetParams { Domain = "some domain", Count = 1 });

            foreach (var item in posts.WallPosts)
            {
                for (int i = 0; i < item.Attachments.Count; i++)
                {
                    Photo items = (Photo)item.Attachments[i].Instance;
                    List<Photo> post = new List<Photo>();
                    post.AddRange(items); // тут ошибку выбивает
                }
             }

post.Add(items) - works, but I need not 1 image, but everything that is in the post, tell me who can implement it