using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace LazyLoding.Model
{
    public class CustomerType
    {
        public int CustomerTypeId { get; set; }
        public string Description { get; set; }

        // 導(dǎo)航屬性使用virtual關(guān)鍵字修飾，用于延遲加載
        public virtual ICollection<Customer> Customers { get; set; }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace LazyLoding.Model
{
    public class Customer
    {
        public int CustomerId { get; set; }
        public string Name { get; set; }

        // 導(dǎo)航屬性使用virtual關(guān)鍵字修飾，用于延遲加載
        public virtual CustomerType CustomerType { get; set; }
        // 導(dǎo)航屬性使用virtual關(guān)鍵字修飾，用于延遲加載
        public virtual CustomerEmail CustomerEmail { get; set; }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace LazyLoding.Model
{
    public class CustomerEmail
    {
        public int CustomerEmailId { get; set; }
        public string Email { get; set; }
        // 導(dǎo)航屬性使用virtual關(guān)鍵字修飾，用于延遲加載
        public virtual Customer Customer { get; set; }
    }
}

using LazyLoding.Model;
using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace LazyLoding.EF
{
    public class Context :DbContext
    {
        public Context()
            : base("name=AppConnection")
        {

        }

        #region 將領(lǐng)域?qū)嶓w添加到DbSet中
        public DbSet<CustomerType> CustomerTypes { get; set; }
        public DbSet<Customer> Customers { get; set; }
        public DbSet<CustomerEmail> CustomerEmails { get; set; }
        #endregion

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            // 設(shè)置表名和主鍵
            modelBuilder.Entity<CustomerType>().ToTable("CustomerType").HasKey(p => p.CustomerTypeId);
            modelBuilder.Entity<Customer>().ToTable("Customer").HasKey(p => p.CustomerId);
            modelBuilder.Entity<CustomerEmail>().ToTable("CustomerEmail").HasKey(p => p.CustomerEmailId);

            // 設(shè)置實(shí)體關(guān)系
            /*
             配置一對(duì)多關(guān)系
             HasMany：表示一個(gè)CustomerType里面包含多個(gè)Customers
             WithRequired：表示必選，CustomerType不能為空
             MapKey：定義實(shí)體之間的外鍵
             */
            modelBuilder.Entity<CustomerType>().HasMany(p => p.Customers).WithRequired(t => t.CustomerType)
                .Map(m =>
                {
                    m.MapKey("CustomerTypeId");
                });

            /*
             配置一對(duì)一的關(guān)系
             HasRequired：表示前者必選包含后者，前者可以獨(dú)立存在，后者不可獨(dú)立存在
             WithRequiredPrincipal：指明實(shí)體的主要 這里表示指定Customer表是主表可以獨(dú)立存在
             MapKey：定義實(shí)體之間的外鍵
             */
            modelBuilder.Entity<Customer>().HasRequired(p => p.CustomerEmail).WithRequiredPrincipal(t => t.Customer)
                .Map(m =>
                {
                    m.MapKey("CustomerId");
                });
            base.OnModelCreating(modelBuilder);
        }
    }
}

namespace LazyLoding.Migrations
{
    using LazyLoding.Model;
    using System;
    using System.Collections.Generic;
    using System.Data.Entity;
    using System.Data.Entity.Migrations;
    using System.Linq;

    internal sealed class Configuration : DbMigrationsConfiguration<LazyLoding.EF.Context>
    {
        public Configuration()
        {
            AutomaticMigrationsEnabled = false;
        }

        protected override void Seed(LazyLoding.EF.Context context)
        {
            //  This method will be called after migrating to the latest version.

            //  You can use the DbSet<T>.AddOrUpdate() helper extension method
            //  to avoid creating duplicate seed data.

            // 初始化種子數(shù)據(jù)
            context.CustomerTypes.AddOrUpdate(
                new CustomerType()
                {
                    Description = "零售",
                    Customers = new List<Customer>()
                     {
                       new Customer(){Name="小喬", CustomerEmail=new CustomerEmail(){ Email="qiao@qq.com"}},
                       new Customer(){Name="周瑜",CustomerEmail=new CustomerEmail(){Email="yu@126.com"}}
                     }
                },
                new CustomerType()
                {
                    Description = "電商",
                    Customers = new List<Customer>()
                  {
                    new Customer(){Name="張飛", CustomerEmail=new CustomerEmail(){Email="zf@qq.com"}},
                    new Customer(){Name="劉備",CustomerEmail=new CustomerEmail(){Email="lb@163.com"}}
                  }
                }
                );
        }
    }
}

// 還沒(méi)有查詢(xún)數(shù)據(jù)庫(kù)
var customerType = dbContext.CustomerTypes;

public Context() : base("name=AppConnection")
{
      // 配置關(guān)閉延遲加載
      this.Configuration.LazyLoadingEnabled = false;
}

//貪婪加載,以下兩種方式都可以 
// 在使用Lambda表達(dá)式指明要加載的導(dǎo)航實(shí)體時(shí)，要引用命名空間:System.Data.Entity
var customers = dbContext.Customers.Include(p => p.CustomerType).Include(p => p.CustomerEmail).ToList();
//方式2
var query = dbContext.Customers.Include("CustomerType").Include("CustomerEmails");