ALGA/zh/Program.cs

using System.Reflection;
using System.Security.Cryptography.X509Certificates;
using System.Xml.Serialization;
using Castle.Components.DictionaryAdapter.Xml;
using Microsoft.EntityFrameworkCore;
using Microsoft.VisualBasic;

namespace zh
{
    public class ProductPackage
    {
        public List<Category> Categories { get; set; } = new List<Category>();
    }
    public class Category
    {
        string Name { get; set; }
        public List<Product> Products = new List<Product>();
    }
    public class Product
    {
        [Requirements(Requirement.RequiredNonEmpty)]
        public string Sku { get; set; }

        public string Name { get; set; }

        [Requirements(Requirement.RequiredNonNegative)]
        public int Price { get; set; }
    }
    public class Program
    {
        public static void Main()
        {
            ProductPackage productackage = new ProductPackage();
            XmlSerializer serializer = new XmlSerializer(typeof(ProductPackage));
            using (StreamReader reader = new StreamReader("zh/products.xml"))
            {
                productackage.Categories = (List<Category>)serializer.Deserialize(reader);
            }
            Shop shop = new Shop();
            shop.Category.AddRange(productackage.Categories);
            shop.SaveChanges();
            List<Product> expensive = new List<Product>();
            foreach (Category category in productackage.Categories)
            {
                expensive.Concat(from x in category.Products
                                 where x.Price > 10000
                                 select x);
            }
        }
    }
    public enum Requirement
    {
        RequiredNonEmpty,
        RequiredNonNegative
    }
    public class RequirementsAttribute : Attribute
    {
        public Requirement Rule { get; set; }
        public RequirementsAttribute(Requirement rule)
        {
            Rule = rule;
        }
    }
    public class Validator
    {
        public static void Validate(Product product)
        {
            var t = product.GetType();
            var p = t.GetProperty("Sku");
            var a = p.GetCustomAttribute<RequirementsAttribute>();
            var v = p.GetValue(product);
            if (a.Rule == Requirement.RequiredNonEmpty)
            {
                if (v == null || (string)v == "")
                {
                    throw new WrongProductException();
                }
            }
            else if(a.Rule == Requirement.RequiredNonNegative)
            {
                if ((int)v < 0)
                {
                    throw new WrongProductException();
                }
            }
        }
    }
    public class WrongProductException : Exception
    {

    }
    public class Shop : DbContext
    {
        //public DbSet<ProductPackage> ProductPackage { get; set; }
        public DbSet<Category> Category { get; set; }
        public DbSet<Product> Product { get; set; }
        public DbSet<Product> Expensive { get; set; }
        public Shop()
        {
            Database.EnsureDeleted();
            Database.EnsureCreated();
        }
        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            string connStr = @"Data Source=(LocalDB)\MSSQLLocalDB;Initial Catalog=Shopdb;Integrated Security=True;MultipleActiveResultSets=true";
            optionsBuilder.UseSqlServer(connStr);
            base.OnConfiguring(optionsBuilder);
        }
    }
}