设计模式：抽象工厂模式（Abstract Factory）

定   义：提供一个创建一系列相关或相互依赖对象的接口，而无需指定它们具体的类。

结构图：

示例结构图：

实体类：

 class User
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }

    class Department
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }

数据访问接口：

 interface IUser
    {
        void Insert(User user);

        User GetUser(int id);
    }

    interface IDepartment
    {
        void Insert(Department department);

        Department GetDepartment(int id);
    }

User数据库访问具体类：

 class SqlServerUser : IUser
    {
        public void Insert(User user)
        {
            Console.WriteLine("向SqlServer数据库中User表添加新用户");
        }

        public User GetUser(int id)
        {
            Console.WriteLine("根据用户Id从SqlServer数据库中获取User");
            return null;
        }
    }

    class AccessUser : IUser
    {
        public void Insert(User user)
        {
            Console.WriteLine("向Access数据库中User表添加新用户");
        }

        public User GetUser(int id)
        {
            Console.WriteLine("根据Id从Access数据库中获取User");
            return null;
        }
    }

Department数据库访问具体类：

 class SqlServerDepartment : IDepartment
    {
        public void Insert(Department department)
        {
            Console.WriteLine("向SqlServer数据库Department表中添加一条新记录");
        }

        public Department GetDepartment(int id)
        {
            Console.WriteLine("根据Id从SqlServer数据库Department表中部门信息");
            return null;
        }
    }

    class AccessDepartment : IDepartment
    {
        public void Insert(Department department)
        {
            Console.WriteLine("向Access数据库Department表中添加一条新记录");
        }

        public Department GetDepartment(int id)
        {
            Console.WriteLine("根据Id从Access数据库Department表中获得部门信息");

            return null;
        }
    }

抽象工厂接口：

interface IFactory
    {
        IUser CreateUser();

        IDepartment CreateDepartment();
    }

SqlServerFactory类：

 class SqlServerFactory : IFactory
    {
        public IUser CreateUser()
        {
            return new SqlServerUser();
        }

        public IDepartment CreateDepartment()
        {
            return new SqlServerDepartment();
        }
    }

AccessFactory类：

 class AccessFactory : IFactory
    {
        public IUser CreateUser()
        {
            return new AccessUser();
        }

        public IDepartment CreateDepartment()
        {
            return new AccessDepartment();
        }
    }

客户端代码：

            User user = new User();
            Department  department=new Department ();

            IFactory factory = new SqlServerFactory();
            IUser iu = factory.CreateUser();
            IDepartment idepart = factory.CreateDepartment();

            iu.Insert(user);
            iu.GetUser();

            idepart.Insert(department);
            idepart.GetDepartment();

工厂方法模式和抽象工厂模式区别：

反射+配置文件方式修改以上示例：

结构图：

配置文件：

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings>
    <add  key="DBType" value="SqlServer"/>
  </appSettings>
</configuration>

DataAccess类：

class DataAccess
    {
        //程序集名称
        private static readonly string AssemblyName = "DesignPatternControl";
        //数据库类型
        private static readonly string db = ConfigurationManager.AppSettings["DBType"];

        public static IUser CreateUser()
        {
            string className = AssemblyName + "." + db + "User"; //具体数据库访问类名称
            return (IUser)Assembly.Load(AssemblyName).CreateInstance(className);
        }

        public static IDepartment CreateDepartment()
        {
            string className = AssemblyName + "." + db + "Department"; //具体数据库访问类名称
            return (IDepartment)Assembly.Load(AssemblyName).CreateInstance(className);
        }
    }

客户端调用：

 //反射+抽象方法
            User user = new User();
            Department department = new Department();

            IUser iu = DataAccess.CreateUser();
            iu.Insert(user);
            iu.GetUser();

            IDepartment id = DataAccess.CreateDepartment();
            id.Insert(department);
            id.GetDepartment();