using System;

using System.Collections.Generic;

using System.ComponentModel.DataAnnotations;

using System.ComponentModel.DataAnnotations.Schema;

using System.Data.Entity;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace ConsoleApplication1

{

    class Program

    {

        public class Site

        {

            [Key]

            public int Id{ get; set; }

            public string Name { get; set; }

            /*virtual 知识点关键字:EF三种关联加载  Lazy Loading,Eager Loading,Explicit Loading*/

            public virtual ICollection<News> Newss { get; set; }

        }

        public class News

        {

            [Key]

            public int Id { get; set; }

            public string title { get; set; }

            public string content { get; set; }

            public virtual Site Site { get; set; }

        }

        public class MyTestContent : DbContext

        {

            public MyTestContent( )

            {

                Database.SetInitializer<MyTestContent>(null);

            }

            public DbSet<Site> Site { get; set; }

            public DbSet<News> News{ get; set; }

        }

        static void saveSiteDemo( )

        {

            using (var db = new MyTestContent())

            {

                db.Site.Add(new Site

                {

                    Name = "新浪"

                });

                db.SaveChanges();

            }

        }

        static void saveSiteDemo( string siteName )

        {

            //首先读取站点实体

            using (var db = new MyTestContent())

            {

                Site site = db.Site.FirstOrDefault(one => one.Name == siteName);

                /*图1:站点下还没有新闻的时候容器为null 所以我们需要new一个出来*/

                if (site.Newss == null)

                {

                    site.Newss = new List<News>();

                }

                /*将需要添加的子集  添加到父集的导航属性中*/

                site.Newss.Add(new News

                {

                    title = "新闻标题",

                    content = "新闻内容"

                });

                /*保存数据库 子集保存完成*/

                db.SaveChanges();

                /*图2:现在来读取子集看看有没有值*/

                News news = db.News.FirstOrDefault();

                /*图3:再来读取父集看看 读取出来的结果与图1有和不同*/

                Site newSite = db.Site.FirstOrDefault();

            }

        }

        static void Main( string[] args )

        {

            saveSiteDemo();

            saveSiteDemo("新浪");

        }