using CZBK.ItcastOA.Model;

 using System;

 using System.Collections.Generic;

 using System.Data.Entity;

 using System.Linq;

 using System.Runtime.Remoting.Messaging;

 using System.Text;

 using System.Threading.Tasks;

 namespace CZBK.ItcastOA.DAL

 {

     public class DbContextFactory

     {

         /// <summary>

         /// 保证EF上下文实例线程内唯一.

         /// </summary>

         /// <returns></returns>

         public static DbContext CreateDbContext()

         {

             DbContext dbContext = (DbContext)CallContext.GetData("db");

             if (dbContext == null)

             {

                 dbContext = new OAEntities();

                 CallContext.SetData("db", dbContext);

             }

             return dbContext;

         }

     }

 }

 public class Singleton

 {

     private static Singleton _instance = null;

     private Singleton(){}

     public static Singleton CreateInstance()

     {

         if(_instance == null)

         {

             _instance = new Singleton();

         }

         return _instance;

     }

 }

 using CZBK.Shop.IDal;

 using System;

 using System.Collections.Generic;

 using System.Linq;

 using System.Text;

 using System.Threading.Tasks;

 namespace CZBK.Shop.DalFactory

 {

     /// <summary>

     /// 工厂模式:解决的就是对象的创建（将对象的创建封装起来）

     /// </summary>

     public class SimpleFactory

     {

         public static IUserInfoDal CreateUserInfoDal()

         {

             return new SqlServerDal.UserInfoDal();

         }

     }

 }

 using System;

 using System.Collections.Generic;

 using System.Configuration;

 using System.Linq;

 using System.Reflection;

 using System.Text;

 using System.Threading.Tasks;

 namespace CZBK.Shop.DalFactory

 {

     /// <summary>

     /// 抽象工厂：本质上与工厂是一样的，都是负责创建对象，但是创建的方式不一样。

     /// </summary>

     public class AbstractFactory

     {

         private static readonly string DalAssembly = ConfigurationManager.AppSettings["DalAssembly"];

         private static readonly string DalNameSpace = ConfigurationManager.AppSettings["DalNameSpace"];

         public static IDal.IUserInfoDal CreateUserInfoDal()

         {

             //通过反射的形式来创建.

             string fullClassName = DalNameSpace + ".UserInfoDal";

             return CreateInstance(fullClassName) as IDal.IUserInfoDal;

         }

         private static object CreateInstance(string fullClassName)

         {

             var assmebly = Assembly.Load(DalAssembly);//加载程序集.

             return assmebly.CreateInstance(fullClassName);

         }

     }

 }