Post_11_2.cs

public IndexViewModel Create()
{
  return new IndexViewModel()
  {
    Categories = this.storage.Categories.ToList().Select(
      c => new CategoryViewModelFactory().Create(c)
    ),
    Articles = this.storage.Articles.OrderBy(a => a.Id).Take(20).ToList().Select(
      a => new ArticleViewModelFactory(this.storage).Create(a)
    )
  };
}

public CategoryViewModel Create(Category category)
{
  return new CategoryViewModel()
  {
    Name = category.Name
  };
}

public ArticleViewModel Create(Article article)
{
  Category category = this.storage.Categories.Find(article.CategoryId);
  Photo photo = this.storage.Photos.FirstOrDefault(ph => ph.ArticleId == article.Id && ph.IsDefault);

  return new ArticleViewModel()
  {
    Category = new CategoryViewModelFactory().Create(category),
    Name = article.Name,
    Price = article.Price,
    Photo = new PhotoViewModelFactory().Create(photo)
  };
}

public PhotoViewModel Create(Photo photo)
{
  return new PhotoViewModel()
  {
    Filename = photo.Filename
  };
}