public int Add(string categoryName)
        {
            var category = new Category { Name = categoryName };

            if (this.categoriesRepo.All().Any(c => c.Name == category.Name))
            {
                return -1;
            }

            this.categoriesRepo.Add(category);
            this.categoriesRepo.SaveChanges();
            return category.Id;
        }
 public int Update(Category category)
 {
     this.categoriesRepo.Update(category);
     this.categoriesRepo.SaveChanges();
     return category.Id;
 }