抽象工廠模式(Abstract Factory)

• 提供一個建立一系列相關或相互依賴物件的介面，而無須指定它們具體的類別。

用簡單工廠來改進抽象工廠

<?xml version="1.0" encoding="utf-8"?>
<configuration>
 <appsettings>
  <add key="DB" value="Access">
 </add></appsettings>
</configuration>

using System;
using System.Reflection;
using System.Configuration;

namespace DPExample
{
 class User
 {
  private int _id;
  public int ID {
   get { return _id; }
   set { _id = value; }
  }

  private string _name;
  public string Name {
   get { return _name; }
   set { _name = value; }
  }
 }

 class Department
 {
  private int _id;
  public int ID {
   get { return _id; }
   set { _id = value; }
  }

  private string _deptName;
  public string DeptName {
   get { return _deptName; }
   set { _deptName = value; }
  }
 }

 interface IUser
 {
  void Insert(User user);
  User GetUser(int id);
 }

 class SqlserverUser : IUser
 {
  public void Insert (User user)
  {
   Console.WriteLine ("在 SQL Server 中給 User 表增加一條紀錄。");
  }

  public User GetUser (int id)
  {
   Console.WriteLine ("在 SQL Server 中根據 ID 得到 User 表一條紀錄。");
   return null;
  }
 }

 class AccessUser : IUser
 {
  public void Insert (User user)
  {
   Console.WriteLine ("在 Access 中給 User 表增加一條紀錄。");
  }

  public User GetUser (int id)
  {
   Console.WriteLine ("在 Access 中根據 ID 得到 Department 表一條紀錄。");
   return null;
  }
 }

 interface IDepartment
 {
  void Insert(Department dept);
  Department GetDepartment(int id);
 }

 class SqlserverDepartment : IDepartment
 {
  public void Insert (Department dept)
  {
   Console.WriteLine ("在 SQL Server 中給 Department 表增加一條紀錄。");
  }

  public Department GetDepartment (int id)
  {
   Console.WriteLine ("在 SQL Server 中根據 ID 得到 Department 表一條紀錄。");
   return null;
  }
 }

 class AccessDepartment : IDepartment
 {
  public void Insert (Department dept)
  {
   Console.WriteLine ("在 Access 中給 Department 表增加一條紀錄。");
  }

  public Department GetDepartment (int id)
  {
   Console.WriteLine ("在 Access 中根據 ID 得到 Department 表一條紀錄。");
   return null;
  }
 }

 class DataAccess
 {
  private static readonly string AssemblyName = "DPExample";
  private static readonly string db = ConfigurationManager.AppSettings["DB"];

  public static IUser CreateUser ()
  {
   string className = AssemblyName + "." + db + "User";
   IUser result = (IUser)Assembly.Load (AssemblyName).CreateInstance (className);
   return result;
  }

  public static IDepartment CreateDepartment ()
  {
   string className = AssemblyName + "." + db + "Department";
   IDepartment result = (IDepartment)Assembly.Load (AssemblyName).CreateInstance (className);
   return result;
  }
 }
}