EF单实对应多表

一、单实体对应多表

　　适用场景主表，拥有相同主键附属表或扩展表。

　　

　1、　建表词句

　　

CREATE TABLE [Chapter2].[Product](
    [SKU] [int] primary key ,
    [Description] [varchar](50) NOT NULL,
    [Price] [decimal](18, 2) NOT NULL)

CREATE TABLE [Chapter2].[ProductWebInfo](
    [SKU] [int] primary key ,
    [ImageURL] [varchar](1024) NULL
) 

　2、新建控制程序，添加EntityFramework 引用。

3、创建Product实体，实体包含两个表组合字段

　　

public class Product
    {
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.None)]
        public int SKU { get; set; }
        public string Description { get; set; }
        public decimal Price { get; set; }
        public string ImageURL { get; set; }
    }

4、新建DbContext子类，注意连接字符串。

public class ProductContext: DbContext
    {
        public DbSet<Product> Products { get; set; }

        public ProductContext() : base("EFRecipesEntities")
        {

        }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
            modelBuilder.Entity<Product>()
                .Map(m =>
                {
                    m.Properties(p => new { p.SKU, p.Description, p.Price });
                    m.ToTable("Product", "Chapter2");
                })
                .Map(m =>
                {
                    m.Properties(p => new { p.SKU, p.ImageURL });
                    m.ToTable("ProductWebInfo", "Chapter2");
                });
        }
    }

注意代码中，Map方法，由多个表组合成单个类配置。

5、修改控制台程序代码

　　

static void Main(string[] args)
        {
            using (var context = new ProductContext())
            {
                var product = new Product
                {
                    SKU = ,
                    Description = "Expandable Hydration Pack",
                    Price = 19.97M,
                    ImageURL = "/pack147.jpg"
                };
                context.Products.Add(product);
                product = new Product
                {
                    SKU = ,
                    Description = "Rugged Ranger Duffel Bag",
                    Price = 39.97M,
                    ImageURL = "/pack178.jpg"
                };
                context.Products.Add(product);
                product = new Product
                {
                    SKU = ,
                    Description = "Range Field Pack",
                    Price = 98.97M,
                    ImageURL = "/noimage.jp"
                };
                context.Products.Add(product);
                product = new Product
                {
                    SKU = ,
                    Description = "Small Deployment Back Pack",
                    Price = 29.97M,
                    ImageURL = "/pack202.jpg"
                };
                context.Products.Add(product);
                context.SaveChanges();
            }
            using (var context = new ProductContext())
            {
                foreach (var p in context.Products)
                {
                    Console.WriteLine("{0} {1} {2} {3}", p.SKU, p.Description,
                        p.Price.ToString("C"), p.ImageURL);
                }
            }

            Console.ReadKey();
        }

　　运行使用SQLProfile查看查询执行语句及结果。

总结：单实体多表时，重写DbContext字类，OnModelCreating方法，在方法中映射(注册)实体属性使用哪些表字段填充。