wewewe

zh/Program.cs

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+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);
+        }
+    }
+}