DbContext

DbContext是EntityFramework很重要的部分，连接域模型与数据库的桥梁，是与数据库通信的主要类。

EF三层构架+接口实现（增删改查）

DbContext主要负责以下活动：

EntitySet:：DbContext包含了所有映射到表的entities

Querying：将Linq-To-Entities转译为Sql并发送到数据库

Change Tracking：从数据库获取entities后保留并跟踪实体数据变化

Persisting Data：根据entity状态执行Insert、update、delete命令

Caching：DbContext的默认第一级缓存，在上下文中的生命周期中存储entity

Manage Relationship：DbContext在DbFirst模式中使用CSDL、MSL、SSDL管理对象关系，Code first中使用fluent api 管理关系

增删改查操作

IDAL

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

namespace ADO.NETEFDemo
{
    public interface IDAL<T> where T : class,new()
    {
        /// <summary>
        /// 增
        /// </summary>
        /// <param name="model"></param>
        /// <returns></returns>
        int Add(T model);

        /// <summary>
        /// 删
        /// </summary>
        /// <param name="whereLambda"></param>
        /// <returns></returns>
        int Delete(Expression<Func<T, bool>> whereLambda);

        /// <summary>
        /// 改
        /// </summary>
        /// <param name="whereLambda"></param>
        /// <param name="propertyNames"></param>
        /// <param name="perpertyValues"></param>
        /// <returns></returns>
        int Update(Expression<Func<T, bool>> whereLambda, string[] propertyNames, object[] perpertyValues);

        /// <summary>
        /// 查
        /// </summary>
        /// <param name="whereLambda"></param>
        /// <returns></returns>
        List<T> GetModelList(Expression<Func<T, bool>> whereLambda);
    }
}

DAL

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

namespace ADO.NETEFDemo
{
    public class DAL<T> : IDAL<T> where T : class,new()
    {
        /// <summary>
        /// 增
        /// </summary>
        /// <param name="model"></param>
        /// <returns></returns>
        public int Add(T model)
        {
            using (testbakEntities db = new testbakEntities())
            {
                db.Set<T>().Add(model);
                return db.SaveChanges();
            }
        }

        /// <summary>
        /// 删
        /// </summary>
        /// <param name="whereLambda"></param>
        /// <returns></returns>
        public int Delete(Expression<Func<T, bool>> whereLambda)
        {
            using (testbakEntities db = new testbakEntities())
            {
                var dbQuery = db.Set<T>();

                //先查询 对应表的 集合
                var list = dbQuery.Where(whereLambda).ToList();

                //遍历集合 里要删除的元素
                foreach (var item in list)
                {
                    //标记为 删除状态
                    dbQuery.Remove(item);
                }
                return db.SaveChanges();
            }
        }

        /// <summary>
        /// 改
        /// </summary>
        /// <param name="whereLambda"></param>
        /// <param name="propertyNames"></param>
        /// <param name="perpertyValues"></param>
        /// <returns></returns>
        public int Update(Expression<Func<T, bool>> whereLambda, string[] propertyNames, object[] perpertyValues)
        {
            using (testbakEntities db = new testbakEntities())
            {
                //1、查询要修改的对象集合
                var list = db.Set<T>().Where<T>(whereLambda).ToList();

                //2、获取要修改的对象的类型
                Type t = typeof(T);

                //3、循环要修改的实体对象，并根据要修改的属性名修改对象对应的属性值
                foreach (var item in list)
                {
                    //循环 要修改的属性 名称， 并 反射取出 t 中的 属性对象
                    for (int index = 0; index < propertyNames.Length; index++)
                    {
                        //获取要修改的属性名
                        string pName = propertyNames[index];

                        //获取属性对象
                        PropertyInfo pi = t.GetProperty(pName);

                        //调用属性对象的 SetValue方法 为当前循环的 item对象 对应的属性赋值
                        pi.SetValue(item, perpertyValues[index], null);
                    }
                }
                return db.SaveChanges();
            }
        }

        /// <summary>
        /// 查
        /// </summary>
        /// <param name="whereLambda"></param>
        /// <returns></returns>
        public List<T> GetModelList(Expression<Func<T, bool>> whereLambda)
        {
            using (testbakEntities db = new testbakEntities())
            {
                return db.Set<T>().Where(whereLambda).ToList();
            }
        }
    }
}

BLL

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

namespace ADO.NETEFDemo
{
    public static class BLL<T> where T : class,new()
    {
        private static IDAL<T> dal = new DAL<T>();

        /// <summary>
        /// 新增
        /// </summary>
        /// <param name="model"></param>
        public static int Add(T model)
        {
            return dal.Add(model);
        }

        /// <summary>
        /// 删除
        /// </summary>
        /// <param name="whereLambda"></param>
        public static int Delete(Expression<Func<T, bool>> whereLambda)
        {
            return dal.Delete(whereLambda);
        }

        /// <summary>
        /// 修改
        /// </summary>
        /// <param name="whereLambda"></param>
        /// <param name="propertyNames"></param>
        /// <param name="perpertyValues"></param>
        /// <returns></returns>
        public static int Update(Expression<Func<T, bool>> whereLambda, string[] propertyNames, object[] perpertyValues)
        {
            return dal.Update(whereLambda, propertyNames, perpertyValues);
        }

        /// <summary>
        /// 查询
        /// </summary>
        /// <param name="whereLambda"></param>
        /// <returns></returns>
        public static List<T> GetModelList(Expression<Func<T, bool>> whereLambda)
        {
            return dal.GetModelList(whereLambda);
        }
    }
}

调用

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

namespace ADO.NETEFDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            GetArticleList();

            AddArticle();

            GetArticleList();

            UpdateArticle();

            GetArticleList();

            DeleteArticel();

            GetArticleList();

            Console.ReadKey();
        }

        /// <summary>
        /// 更新
        /// </summary>
        private static void UpdateArticle()
        {
            int result = BLL<t_crobot_reship_articles>
                .Update(e => e.title.Contains("EF"), new[] { "title", "update_time" }, 
                        new object[] { "我是使用EF修改过标题的文章", DateTime.Now });
            if (result >= 0)
            {
                Console.WriteLine("更新成功");
            }
            else
            {
                Console.WriteLine("更新失败");
            }
            Console.WriteLine();
        }

        /// <summary>
        /// 删除
        /// </summary>
        private static void DeleteArticel()
        {
            int result = BLL<t_crobot_reship_articles>.Delete(e => e.title.Contains("EF"));
            if (result >= 0)
            {
                Console.WriteLine("删除成功");
            }
            else
            {
                Console.WriteLine("删除失败");
            }
            Console.WriteLine();
        }

        /// <summary>
        /// 新增
        /// </summary>
        private static void AddArticle()
        {
            t_crobot_reship_articles model = new t_crobot_reship_articles();
            model.create_time = DateTime.Now;
            model.module_id = 1;
            model.adword_id = 20;
            model.pick_id = 1;
            model.vote_id = "1";
            model.title = "我是使用EF添加的文章";
            model.content_id = 1;
            model.release_url = "http://www.sss.com";
            model.state = true;
            int result = BLL<t_crobot_reship_articles>.Add(model);
            if (result >= 0)
            {
                Console.WriteLine("新增成功");
            }
            else
            {
                Console.WriteLine("新增失败");
            }
            Console.WriteLine();
        }

        /// <summary>
        /// 获取文章列表
        /// </summary>
        private static void GetArticleList()
        {
            List<t_crobot_reship_articles> articleList = BLL<t_crobot_reship_articles>
                .GetModelList(e => e.state == true);

            Console.WriteLine("文章总数：" + articleList.Count.ToString());
            foreach (t_crobot_reship_articles model in articleList)
            {
                Console.WriteLine("标题：" + model.title);
            }

            Console.WriteLine();
        }
    }
}

结果

EF三层构架+接口实现（增删改查）

EF三层构架+接口实现（增删改查）

DbContext

增删改查操作

IDAL

DAL

BLL

调用

结果

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