EF Code First一对一、一对多、多对多关联关系配置

1、EF Code First一对一关联关系

 　　项目结构图：

　　实体类：

　　Account.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;



namespace Northwind.App.Entities

{

   public class Account

    {

       /// <summary>

       /// 账户ID

       /// </summary>

       public int AccountID { get; set; }



       /// <summary>

       /// 账户名

       /// </summary>

       public string AccountName { get; set; }



       /// <summary>

       /// 密码

       /// </summary>

       public string Password { get; set; }



       /// <summary>

       /// 用户信息

       /// </summary>

       public virtual User User { get; set; }

    }

}

　　User.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;



namespace Northwind.App.Entities

{

   public class Account

    {

       /// <summary>

       /// 账户ID

       /// </summary>

       public int AccountID { get; set; }



       /// <summary>

       /// 账户名

       /// </summary>

       public string AccountName { get; set; }



       /// <summary>

       /// 密码

       /// </summary>

       public string Password { get; set; }



       /// <summary>

       /// 用户信息

       /// </summary>

       public virtual User User { get; set; }

    }

}

　　实体映射类：

　　AccountMap.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;



using System.Data.Entity.ModelConfiguration;

using System.ComponentModel.DataAnnotations.Schema;



using Northwind.App.Entities;



namespace Northwind.App.Mapping

{

    public class AccountMap : EntityTypeConfiguration<Account>

    {

        public AccountMap()

        {

            // Primary Key

            this.HasKey(t => t.AccountID);



            // Properties

            this.Property(t => t.AccountName).HasMaxLength(50);

            this.Property(t => t.Password).HasMaxLength(100);



            // Table & Column Mappings

            this.ToTable("Account");

            this.Property(t => t.AccountID).HasColumnName("AccountID");

            this.Property(t => t.AccountName).HasColumnName("AccountName");

            this.Property(t => t.Password).HasColumnName("Password");

        }

    }

}

　　UserMap.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;



using System.Data.Entity.ModelConfiguration;

using System.ComponentModel.DataAnnotations.Schema;



using Northwind.App.Entities;



namespace Northwind.App.Mapping

{

    public class UserMap : EntityTypeConfiguration<User>

    {

        public UserMap()

        {

            // Primary Key

            this.HasKey(t => t.AccountID);



            // Properties

            this.Property(t => t.AccountID).HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);

            this.Property(t => t.UserName).HasMaxLength(50);

            this.Property(t => t.Email).HasMaxLength(100);



            // Table & Column Mappings

            this.ToTable("User");

            this.Property(t => t.AccountID).HasColumnName("AccountID");

            this.Property(t => t.UserName).HasColumnName("UserName");

            this.Property(t => t.Email).HasColumnName("Email");

            this.Property(t => t.RegisterDate).HasColumnName("RegisterDate");



            // Relationships

            this.HasRequired(t => t.Account)

                .WithRequiredDependent(t => t.User);

        }

    }

}

　　NorthwindContext.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;



using System.Data.Entity;



using Northwind.App.Entities;

using Northwind.App.Mapping;



namespace Northwind.App

{

    public class NorthwindContext : DbContext

    {

        static NorthwindContext()

        {

            Database.SetInitializer(new DropCreateDatabaseIfModelChanges<NorthwindContext>());

        }



        public DbSet<Account> Accounts { get; set; }

        public DbSet<User> Users { get; set; }



        protected override void OnModelCreating(DbModelBuilder modelBuilder)

        {

            modelBuilder.Configurations.Add(new AccountMap());

            modelBuilder.Configurations.Add(new UserMap());

        }

    }

}

　　Program.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;



using Northwind.App.Entities;



namespace Northwind.App

{

    class Program

    {

        static void Main(string[] args)

        {

            using (NorthwindContext db = new NorthwindContext())

            {

                Account account = new Account { AccountName = "Test", Password = "1" };

                db.Accounts.Add(account);



                User user = new User { AccountID = account.AccountID, UserName = "测试", Email = "[email protected]", RegisterDate = DateTime.Now };

                db.Users.Add(user);



                db.SaveChanges();

            }

        }

    }

}

　　代码运行后生成的数据库结构图：

 

2、EF Code First一对多关联关系

　　关联表：Product 产品表、Category分类表

　　关联关系：一个产品属于一个分类，一个分类可以有多个产品

　　实体代码：

　　Category.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;



namespace Northwind.App.Entities

{

    public class Category

    {

        /// <summary>

        /// 分类ID

        /// </summary>

        public Guid CategoryID { get; set; }



        /// <summary>

        /// 分类名称

        /// </summary>

        public string CategoryName { get; set; }



        /// <summary>

        /// 产品

        /// </summary>

        public virtual ICollection<Product> Products { get; set; }

    }

}

　　Product.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;



namespace Northwind.App.Entities

{

    public class Product

    {

        /// <summary>

        /// 产品ID

        /// </summary>

        public Guid ProductID { get; set; }



        /// <summary>

        /// 产品名称

        /// </summary>

        public string ProductName { get; set; }



        /// <summary>

        /// 单价

        /// </summary>

        public decimal UnitPrice { get; set; }



        /// <summary>

        /// 数量

        /// </summary>

        public Nullable<int> Quantity { get; set; }



        /// <summary>

        /// 库存

        /// </summary>

        public Nullable<int> UnitsInStock { get; set; }



        /// <summary>

        /// 产品类别ID

        /// </summary>

        public Guid CategoryID { get; set; }



        /// <summary>

        /// 产品类别

        /// </summary>

        public virtual Category Category { get; set; }

    }

}

　　实体映射类：

　　CategoryMap.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;



using System.Data.Entity.ModelConfiguration;

using System.ComponentModel.DataAnnotations.Schema;



using Northwind.App.Entities;



namespace Northwind.App.Mapping

{

    public class CategoryMap : EntityTypeConfiguration<Category>

    {

        public CategoryMap()

        {

            // Primary Key

            this.HasKey(t => t.CategoryID);



            // Properties

            this.Property(t => t.CategoryID)

                .HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);

            this.Property(t => t.CategoryName).IsRequired()

                .HasMaxLength(100);



            // Table & Column Mappings

            this.ToTable("Category");

            this.Property(t => t.CategoryID).HasColumnName("CategoryID");

            this.Property(t => t.CategoryName).HasColumnName("CategoryName");

        }

    }

}

　　ProductMap.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;



using System.Data.Entity.ModelConfiguration;

using System.ComponentModel.DataAnnotations.Schema;



using Northwind.App.Entities;



namespace Northwind.App.Mapping

{

    public class ProductMap : EntityTypeConfiguration<Product>

    {

        public ProductMap()

        {

            // Primary Key

            this.HasKey(t => t.ProductID);



            // Properties

            this.Property(t => t.ProductID)

                .HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);

            this.Property(t => t.ProductName).IsRequired()

                .HasMaxLength(100);

            this.Property(t => t.UnitPrice).HasPrecision(10, 2);



            // Table & Column Mappings

            this.ToTable("Product");

            this.Property(t => t.ProductID).HasColumnName("ProductID");

            this.Property(t => t.ProductName).HasColumnName("ProductName");

            this.Property(t => t.UnitPrice).HasColumnName("UnitPrice");

            this.Property(t => t.Quantity).HasColumnName("Quantity");

            this.Property(t => t.UnitsInStock).HasColumnName("UnitsInStock");

            this.Property(t => t.CategoryID).HasColumnName("CategoryID");



            // Relationships

            this.HasRequired(t => t.Category)

                .WithMany(t => t.Products)

                .HasForeignKey(t => t.CategoryID)

                .WillCascadeOnDelete(false);

        }

    }

}

　　NorthwindContext.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;



using System.Data.Entity;



using Northwind.App.Entities;

using Northwind.App.Mapping;



namespace Northwind.App

{

    public class NorthwindContext : DbContext

    {

        static NorthwindContext()

        {

            Database.SetInitializer(new DropCreateDatabaseIfModelChanges<NorthwindContext>());

        }



        public DbSet<Account> Accounts { get; set; }

        public DbSet<User> Users { get; set; }

        public DbSet<Category> Categories { get; set; }

        public DbSet<Product> Products { get; set; }



        protected override void OnModelCreating(DbModelBuilder modelBuilder)

        {

            modelBuilder.Configurations.Add(new AccountMap());

            modelBuilder.Configurations.Add(new UserMap());

            modelBuilder.Configurations.Add(new CategoryMap());

            modelBuilder.Configurations.Add(new ProductMap());

        }

    }

}

　　Program.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;



using Northwind.App.Entities;



namespace Northwind.App

{

    class Program

    {

        static void Main(string[] args)

        {

            using (NorthwindContext db = new NorthwindContext())

            {

                Category category = new Category { CategoryName = "手机数码" };

                db.Categories.Add(category);



                Product product = new Product { CategoryID = category.CategoryID, ProductName = "IPhone5", UnitPrice = 5000m, Quantity = 100, UnitsInStock = 60 };

                db.Products.Add(product);



                db.SaveChanges();

            }

        }

    }

}

　　运行代码后生成的数据表：