<connectionStrings>

<add name="XxzxWorkEntities" connectionString="metadata=res://*/fenlei.csdl|res://*/fenlei.ssdl|res://*/fenlei.msl;provider=System.Data.SqlClient;provider connection string="data source=localhost;initial catalog=XxzxWork;user id=sa;password=123!@#;MultipleActiveResultSets=True;App=EntityFramework"" providerName="System.Data.EntityClient" />

</connectionStrings>

using System;

using System.Collections.Generic;

using System.Data.Entity;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace EFtest

{

    class Program

    {

        static void Main(string[] args)

        {

            var db = new XxzxWorkEntities();

            //删除

            var  fenleiDel = db.CategoryMaintenance.First(p => p.ID == "666");

            db.CategoryMaintenance.Remove(fenleiDel);

            db.SaveChanges();

            //新增

            var newfenlei = new CategoryMaintenance();

            newfenlei.ID = "666";

            newfenlei.Name = "666";

            newfenlei.ParentID = "top";

            newfenlei.ContentType = "内容";

            newfenlei.IsEffective = "是";

            db.CategoryMaintenance.Add(newfenlei);

            db.SaveChanges();

            //修改

            var fenleiObj = db.CategoryMaintenance.First(a => a.ID == "666");

            fenleiObj.Name = "666被修改22";

            db.CategoryMaintenance.Attach(fenleiObj);

            db.Entry(fenleiObj).State = EntityState.Modified;

            db.SaveChanges();

            //查询

            var Item = db.CategoryMaintenance.Where(a =>a.ParentID=="top" && a.IsEffective=="是").OrderBy(a => a.ID).ToList();

            foreach (var fenlei in Item)

            {

                if (fenlei.Name.ToString()=="测试")

                {

                    //跨表查询

                    var subItem = db.XxzxMainMsg.Where(b => b.BigFl == "主栏目"&&b.IsDeleted == null && b.SmallFl == fenlei.Name.ToString());

                    Console.Write(fenlei.Name + "\n");

                    foreach (var subneirong in subItem)

                    {

                        Console.Write(subneirong.STitle + "\n");

                    }

                }

            }

            Console.ReadKey();

        }

    }

}