EntityFramework 6

3.EF6

3.1初步目录及说明

下面是用VS2013开发环境创建的项目:

说明:控制台项目类型,安装 EF版本为6.1.3 , 数据库连接字符串配置:

隐藏代码  <connectionStrings>

    <add name="DefaultConnection"

         connectionString="Data Source=.;Initial Catalog=TestDB;UID=sa;PWD=123456"

      providerName="System.Data.SqlClient" />

  </connectionStrings>

EFContext.cs代码:

隐藏代码using Consoles.EF6.Models;

using System.Data.Entity;

namespace Consoles.EF6.Repositories

{

    public class EFContext : DbContext

    {

        public EFContext() : base("DefaultConnection") { }

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

        protected override void OnModelCreating(DbModelBuilder modelBuilder)

        {

            modelBuilder.Entity<Category>().HasKey(k => k.CategoryId) //设置主键

                .Property(q => q.CategoryName).IsRequired();//设置不能为空

        }

    }

}

注:

a.数据库上下文构造方法 ,继承基类,其参数是DefaultConnection,配置的数据库连接字符串中name值要一致 ;

如果name值和上下文类名(EFContext)一致的话,上下文类的构造方法也可以省略 .

b.为了保持实体类" 干净 ",不使用 DataAnnotations 数据注解特性,改为 Fluent API 配置方式.当然有些已经默认了,我们照样进行配置.

如:属性为 Id(字母不分大小写)或为类名+Id ,它会默认为主键,但我们也配置:Entity<Category>().HasKey(k => k.CategoryId)

疑问：这种两种方式，到底采用那种好呢？这个……我表示无语，你自个看那个爽啦。

3.2示例一

Category.cs代码：

隐藏代码namespace Consoles.EF6.Models

{

    public class Category

    {

        public int CategoryId { get; set; }

        public string CategoryName { get; set; }

        public string Description { get; set; }

    }

}

Program.cs代码：

隐藏代码using Consoles.EF6.Models;

using Consoles.EF6.Repositories;

using System;

using System.Collections.Generic;

using System.Linq;

using System.Data.Entity.Migrations;

namespace Consoles.EF6

{

    class Program

    {

        static void Main(string[] args)

        {

            #region 示例一

            using (var db = new EFContext())

            {

                var categories = new List<Category>

                {

                    new Category(){ CategoryName="Mobile",Description="手机大类"},

                    new Category(){ CategoryName="Computer",Description="电脑大类"}

                };

                //AddOrUpdate:根据指定列,相同就更新,不相同就添加

                categories.ForEach(list => db.Categories.AddOrUpdate(c => c.CategoryId, list));

                db.SaveChanges();

                //var query = db.Categories;

                 var query = from c in db.Categories select c;

                //遍历输出

                foreach (var item in query)

                {

                    Console.WriteLine("类别:{0};说明:{1}", item.CategoryName, item.Description);

                }

            }

            #endregion

            Console.ReadKey();

        }

    }

}

运行结果：

查看数据库：

3.3示例二

我们添一个 Subcategory.cs ，其代码：

隐藏代码namespace Consoles.EF6.Models

{

    public class Subcategory

    {

        public int SubcategoryId { get; set; }

        public string SubcategoryName { get; set; }

        public int CategoryId { get; set; }

        public Category Category { get; set; }

    }

}

再修改 Category.cs 代码：

隐藏代码using System.Collections.Generic;

namespace Consoles.EF6.Models

{

    public class Category

    {

        public int CategoryId { get; set; }

        public string CategoryName { get; set; }

        public string Description { get; set; }

        public ICollection<Subcategory> Subcategories { get; set; }

    }

}

设计关系为：大类Category：子类Subcategory=1：N。子类必须属于某一个大类，也就是外键不能为空。配置 Fluent API

隐藏代码using Consoles.EF6.Models;

using System.Data.Entity;

namespace Consoles.EF6.Repositories

{

    public class EFContext : DbContext

    {

        public EFContext() : base("DefaultConnection") { }

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

        public DbSet<Subcategory> Subcategories { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)

        {

            modelBuilder.Entity<Category>().HasMany(s => s.Subcategories)

                .WithRequired(c => c.Category).HasForeignKey(f=>f.CategoryId);

            modelBuilder.Entity<Category>().HasKey(k => k.CategoryId);

            modelBuilder.Entity<Category>().Property(p => p.CategoryName).HasMaxLength(20);

            modelBuilder.Entity<Subcategory>().HasKey(K => K.SubcategoryId);

            modelBuilder.Entity<Subcategory>().Property(p => p.SubcategoryName).IsRequired();

        }

    }

}

Program.cs代码：

隐藏代码using Consoles.EF6.Models;

using Consoles.EF6.Repositories;

using System;

using System.Collections.Generic;

using System.Linq;

using System.Data.Entity.Migrations;

namespace Consoles.EF6

{

    class Program

    {

        static void Main(string[] args)

        {

            #region 示例二

            using (var db = new EFContext())

            {

                var categories = new List<Category>

                {

                    new Category(){ CategoryName="Mobile",Description="手机大类"},

                    new Category(){ CategoryName="Computer",Description="电脑大类"}

                };

                categories.ForEach(list => db.Categories.AddOrUpdate(c => c.CategoryId, list));

                db.SaveChanges();

                var subcategories = new List<Subcategory>

                {

                    new Subcategory(){ SubcategoryName="2G",Category=db.Categories.Single(c=>c.CategoryName=="Mobile")},

                    new Subcategory(){ SubcategoryName="3G",Category=db.Categories.Single(c=>c.CategoryName=="Mobile")},

                    new Subcategory(){ SubcategoryName="4G",Category=db.Categories.Single(c=>c.CategoryName=="Mobile")},

                    new Subcategory(){ SubcategoryName="Desktop",Category=db.Categories.Single(c=>c.CategoryName=="Computer")},

                    new Subcategory(){ SubcategoryName="Tablet ",Category=db.Categories.Single(c=>c.CategoryName=="Computer")}

                };

                subcategories.ForEach(list => db.Subcategories.AddOrUpdate(c => c.SubcategoryId, list));

                db.SaveChanges();

                var query = from c in db.Categories select c;

                foreach (var item in query)

                {

                    Console.WriteLine("类别:{0};说明:{1}", item.CategoryName, item.Description);

                }

            }

            #endregion

            Console.ReadKey();

        }

    }

}

查看数据库：

嘎嘎！一对多关系OK!Subcategories表的外键也不为空！

3.4示例三

我们再添加一个 Product.cs ，其代码：

隐藏代码using System.Collections.Generic;

namespace Consoles.EF6.Models

{

    public class Product

    {

        public int ProductId { get; set; }

        public string ProductName { get; set; }

        public ICollection<Subcategory> Subcategories { get; set; }

    }

}

再修改 Subcategory.cs：

隐藏代码using System.Collections.Generic;

namespace Consoles.EF6.Models

{

    public class Subcategory

    {

        public int SubcategoryId { get; set; }

        public string SubcategoryName { get; set; }

        public int CategoryId { get; set; }

        public Category Category { get; set; }

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

    }

}

修改 EFContext.cs:

隐藏代码using Consoles.EF6.Models;

using System.Data.Entity;

namespace Consoles.EF6.Repositories

{

    public class EFContext : DbContext

    {

        public EFContext() : base("DefaultConnection") { }

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

        public DbSet<Subcategory> Subcategories { get; set; }

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

        protected override void OnModelCreating(DbModelBuilder modelBuilder)

        {

            modelBuilder.Entity<Category>().HasMany(s => s.Subcategories)

                .WithRequired(c => c.Category).HasForeignKey(f => f.CategoryId);

            modelBuilder.Entity<Category>().HasKey(k => k.CategoryId);

            modelBuilder.Entity<Category>().Property(p => p.CategoryName).HasMaxLength(20);

            modelBuilder.Entity<Subcategory>().HasKey(K => K.SubcategoryId);

            modelBuilder.Entity<Subcategory>().Property(p => p.SubcategoryName).IsRequired();

            modelBuilder.Entity<Product>().HasKey(k => k.ProductId);

            modelBuilder.Entity<Product>().Property(p => p.ProductName).HasMaxLength(120);

            modelBuilder.Entity<Subcategory>()

             .HasMany(c => c.Products).WithMany(p => p.Subcategories)

             .Map(t => t.MapLeftKey("SubCategoryId")

             .MapRightKey("ProductId")

             .ToTable("SubcategoryProduct"));

        }

    }

}

查看数据库：

3.5初始化数据

前面我们是在 Main 方法写的模拟数据代码，是不是不太好？在“ 第05章 ”文中，我也说过有预留的问题，在这补充一下。

添加 SampleData.cs ，其代码：

隐藏代码using Consoles.EF6.Models;

using System.Collections.Generic;

using System.Data.Entity;

using System.Linq;

using System.Data.Entity.Migrations;

namespace Consoles.EF6.Repositories

{

    public class SampleData : DropCreateDatabaseIfModelChanges<EFContext>

    {

        protected override void Seed(EFContext db)

        {

            var categories = new List<Category>

                {

                    new Category(){ CategoryName="Mobile",Description="手机大类"},

                    new Category(){ CategoryName="Computer",Description="电脑大类"}

                };

            categories.ForEach(list => db.Categories.AddOrUpdate(c => c.CategoryId, list));

            db.SaveChanges();

            var subcategories = new List<Subcategory>

                {

                    new Subcategory(){ SubcategoryName="2G",Category=db.Categories.Single(c=>c.CategoryName=="Mobile")},

                    new Subcategory(){ SubcategoryName="3G",Category=db.Categories.Single(c=>c.CategoryName=="Mobile")},

                    new Subcategory(){ SubcategoryName="4G",Category=db.Categories.Single(c=>c.CategoryName=="Mobile")},

                    new Subcategory(){ SubcategoryName="Desktop",Category=db.Categories.Single(c=>c.CategoryName=="Computer")},

                    new Subcategory(){ SubcategoryName="Tablet ",Category=db.Categories.Single(c=>c.CategoryName=="Computer")}

                };

            subcategories.ForEach(list => db.Subcategories.AddOrUpdate(c => c.SubcategoryId, list));

            db.SaveChanges();

        }

    }

}

注:关于多对多关系的数据添加,参加" 第05章 "示例!

添加配置节点：

这样只要有访问数据库时，就会初始化数据了，如：

隐藏代码using Consoles.EF6.Models;

using Consoles.EF6.Repositories;

using System;

using System.Collections.Generic;

using System.Linq;

using System.Data.Entity.Migrations;

namespace Consoles.EF6

{

    class Program

    {

        static void Main(string[] args)

        {

            using (var db = new EFContext())

            {

                var query = from c in db.Categories select c;

                foreach (var item in query)

                {

                    Console.WriteLine("类别:{0};说明:{1}", item.CategoryName, item.Description);

                }

            }

            Console.ReadKey();

        }

    }

}

我们并没在程序显式的代码中执行SampleData里的Seed方法,通过配置文件即可 (在不需要时,也可以 disableDatabaseInitialization 关闭).

4.EF7

4.1目录及说明

下面是用 VS2015 开发环境创建的项目:

说明：ASP.NET 5版的 WebApi 项目类型；

依赖和Commands配置：

commands之ef是迁移用的，这在“第06章”已经介绍过，这里会略过。

4.2示例

由于EF7暂时不直接支持多对多实体关系（也可能我了解有限），所以这里举例一对多。

Category.cs代码：

隐藏代码using System.Collections.Generic;

namespace WebApies.EF7.Models

{

    public class Category

    {

        public int CategoryId { get; set; }

        public string CategoryName { get; set; }

        public string Description { get; set; }

        public ICollection<Subcategory> Subcategories { get; set; }

    }

}

Subcategory.cs代码：

隐藏代码namespace WebApies.EF7.Models

{

    public class Subcategory

    {

        public int SubcategoryId { get; set; }

        public string SubcategoryName { get; set; }

        public int CategoryId { get; set; }

        public Category Category { get; set; }

    }

}

EFContext.cs代码：

隐藏代码using Microsoft.Data.Entity;

using WebApies.EF7.Models;

using Microsoft.Data.Entity.Metadata;

namespace WebApies.EF7.Repositories

{

    public class EFContext : DbContext

    {

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

        public DbSet<Subcategory> Subcategories { get; set; }

        protected override void OnConfiguring(DbContextOptions options)

        {

            options.UseSqlServer(

                "Server=(localdb)\\mssqllocaldb;Database=TestDB;Trusted_Connection=True;MultipleActiveResultSets=true");

        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)

        {

            modelBuilder.Entity<Category>().HasMany(C => C.Subcategories).WithOne().ForeignKey(f=>f.CategoryId);

            modelBuilder.Entity<Category>().Key(k => k.CategoryId);

            modelBuilder.Entity<Category>().Property(p => p.CategoryName).MaxLength(20);

            modelBuilder.Entity<Subcategory>().Key(K => K.SubcategoryId);

            modelBuilder.Entity<Subcategory>().Property(p => p.SubcategoryName).Required();

        }

    }

}

迁移完毕后，查看数据库：

注：MaxLength没有起作用！（完整版的sqlserver是正常的）

基架模板代码创建：

此时目录：

这是 T4模板代码，这个MVC版的，webapi版本的还得等等了!