EF單實對應多表

 

1、單實體對應多表

　　適用場景主表，擁有相同主鍵附屬表或擴展表。

　　

　一、　建表詞句

　　

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
) 

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　二、新建控制程序，添加EntityFramework 引用。

   三、建立Product實體，實體包含兩個表組合字段

　　

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; }
    }

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   四、新建DbContext子類，注意鏈接字符串。     

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");
                });
        }
    }

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    注意代碼中，Map方法，由多個表組合成單個類配置。

    

 

      五、修改控制檯程序代碼

　　

static void Main(string[] args)
        {
            using (var context = new ProductContext())
            {
                var product = new Product
                {
                    SKU = 147,
                    Description = "Expandable Hydration Pack",
                    Price = 19.97M,
                    ImageURL = "/pack147.jpg"
                };
                context.Products.Add(product);
                product = new Product
                {
                    SKU = 178,
                    Description = "Rugged Ranger Duffel Bag",
                    Price = 39.97M,
                    ImageURL = "/pack178.jpg"
                };
                context.Products.Add(product);
                product = new Product
                {
                    SKU = 186,
                    Description = "Range Field Pack",
                    Price = 98.97M,
                    ImageURL = "/noimage.jp"
                };
                context.Products.Add(product);
                product = new Product
                {
                    SKU = 202,
                    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();
        }

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　　運行使用SQLProfile查看查詢執行語句及結果。

 

總結：單實體多表時，重寫DbContext字類，OnModelCreating方法，在方法中映射(註冊)實體屬性使用哪些表字段填充。