利用简单工厂模式来改进抽象工厂使用的复杂性（抽象工厂详见 设计模式之—抽象工厂模式）
数据表（User）业务处理接口（IUser）
namespace FactoryMethodPatternDB.CLASS
{
interface IUser
{
void Insert(User user);
void GetUser(string id);
}
}
数据表（Department）业务处理接口（IDepartment）
namespace FactoryMethodPatternDB.CLASS
{
interface IDepartment
{
void Insert(Department dept);
void GetDept(string id);
}
}
SQL操作表（User）类（SqlServerUser）
namespace FactoryMethodPatternDB.CLASS
{
class SqlServerUser:IUser
{
public void Insert(User user)
{
Console.WriteLine("在User表中插入一条数据{0}！SQL数据库",user);
} public void GetUser(string id)
{
Console.WriteLine("通过{0}来查找数据！SQL数据库", id);
}
}
}
SQL操作表（Department）类（SqlServerDepartment）
namespace FactoryMethodPatternDB.CLASS
{
class SqlServerDepartment:IDepartment
{
public void Insert(Department dept)
{
Console.WriteLine("在{0}表中插入数据！SQL数据库", dept);
}
public void GetDept(string id)
{
Console.WriteLine("通过{0}查找数据库表！SQL数据库", id);
} }
}
ACCESS操作表（User）类（AccessUser）
namespace FactoryMethodPatternDB.CLASS
{
class AccessUser:IUser
{
public void Insert(User user)
{
Console.WriteLine("在{0}表中插入数据！Access数据库",user);
}
public void GetUser(string id)
{
Console.WriteLine("通过{0}查找数据库表！Access数据库",id);
}
}
}
ACCESS操作表（Department）类（AccessDepartment）
namespace FactoryMethodPatternDB.CLASS
{
class AccessDepartment:IDepartment
{
public void Insert(Department dept)
{
Console.WriteLine("在{0}表中插入数据！Access数据库", dept);
}
public void GetDept(string id)
{
Console.WriteLine("通过{0}查找数据库表！Access数据库", id);
}
}
}
工厂接口和工厂类被SelectDB替换：
namespace FactoryMethodPatternDB
{
class SelectDB
{
//private static readonly string db = "Sqlserver";
private static readonly string db = "Access";
public static IUser CreateUser()
{
IUser iuser = null;
switch (db)
{
case "Sqlserver":
iuser = new SqlServerUser();
break;
case "Access":
iuser = new AccessUser();
break;
}
return iuser;
} public static IDepartment CreateDept()
{
IDepartment idept = null;
switch (db)
{
case "Sqlserver":
idept = new SqlServerDepartment();
break;
case "Access":
idept = new AccessDepartment();
break;
}
return idept;
}
}
}
简单工厂模式测试类
//简单工厂与抽象工厂模式相结合
User user = new User();
Department dept = new Department();
IUser iuser = SelectDB.CreateUser();
iuser.Insert(user);
iuser.GetUser("ID");
IDepartment idept = SelectDB.CreateDept();
idept.Insert(dept);
idept.GetDept("name");
若增加Oracle数据库，则需要更改Switch语句块 违背开放-封闭原则。解决此问题的方法是采用反射
将SelectDB换成反射类（Reflection）
添加反射引用命名空间using System.Reflection;
using System.Reflection;
namespace FactoryMethodPatternDB
{
class Reflection
{
private static readonly string AssemblyName = "FactoryMethodPatternDB"; //程序集
private static readonly string db = "SqlServer"; //业务类的名称为SqlServer + 表名 如（SqlServerUser）方便反射使用 public static IUser CreateUser()
{
string className = AssemblyName + ".CLASS." + db + "User"; //类名（带命名空间）
return (IUser)Assembly.Load(AssemblyName).CreateInstance(className);
} public static IDepartment CreateDept()
{
string className = AssemblyName + "." + "Department";
return (IDepartment)Assembly.Load(AssemblyName).CreateInstance(className);
}
}
}
反射测试类
//反射与抽象工厂模式相结合
User user = new User();
Department dept = new Department();
IUser iuser = Reflection.CreateUser();
iuser.Insert(user);
iuser.GetUser("ID"); IDepartment idept = Reflection.CreateDept();
idept.Insert(dept);
idept.GetDept("Name");