乐在其中设计模式(C#) - 装饰模式(Decorator Pattern)
作者： 介绍 动态地给一个对象添加一些额外的职责。就扩展功能而言，它比生成子类方式更为灵活。 示例 有一个Message实体类，某个对象对它的操作有Insert()和Get()方法，现在扩展这个对象的功能。 
MessageModel 
using System; using System.Collections.Generic; using System.Text; namespace Pattern.Decorator
{ 
/**//// <summary>
/// Message实体类
/// </summary> public class MessageModel { /**//// <summary> /// 构造函数 /// </summary> /// <param name="msg">Message内容</param> /// <param name="pt">Message发布时间</param> public MessageModel(string msg, DateTime pt) { this._message = msg; this._publishTime = pt; } private string _message; /**//// <summary> /// Message内容 /// </summary> public string Message { get { return _message; } set { _message = value; } } private DateTime _publishTime; /**//// <summary> /// Message发布时间 /// </summary> public DateTime PublishTime { get { return _publishTime; } set { _publishTime = value; } } }
} using System; using System.Collections.Generic; using System.Text; namespace Pattern.Decorator { /**//// <summary> /// 操作Message的抽象构件（Component） /// </summary> public abstract class AbstractMessage { /**//// <summary> /// 获取Message /// </summary> /// <returns></returns> public abstract List<MessageModel> Get(); /**//// <summary> /// 插入Message /// </summary> /// <param name="mm">Message实体对象</param> /// <returns></returns> public abstract bool Insert(MessageModel mm); }} using System; using System.Collections.Generic; using System.Text; namespace Pattern.Decorator { /**//// <summary> /// Sql方式操作Message（ConcreteComponent） /// </summary> public class SqlMessage : AbstractMessage { /**//// <summary> /// 获取Message /// </summary> /// <returns></returns> public override List<MessageModel> Get() { List<MessageModel> l = new List<MessageModel>(); l.Add(new MessageModel("SQL方式获取Message", DateTime.Now)); return l; } /**//// <summary> /// 插入Message /// </summary> /// <param name="mm">Message实体对象</param> /// <returns></returns> public override bool Insert(MessageModel mm) { // 代码略 return true; } }} using System; using System.Collections.Generic; using System.Text; namespace Pattern.Decorator { /**/ /// <summary> /// Xml方式操作Message（ConcreteComponent） /// </summary> public class XmlMessage : AbstractMessage { /**/ /// <summary> /// 获取Message /// </summary> /// <returns></returns> public override List < MessageModel > Get() { List < MessageModel > l = new List < MessageModel > (); l.Add( new MessageModel( " XML方式获取Message " , DateTime.Now)); return l; } /**/ /// <summary> /// 插入Message /// </summary> /// <param name="mm"> Message实体对象 </param> /// <returns></returns> public override bool Insert(MessageModel mm) { // 代码略 return true ; } } } using System; using System.Collections.Generic; using System.Text; namespace Pattern.Decorator { /**//// <summary> /// 装饰AbstractMessage（Decorator） /// </summary> public abstract class AbstractMessageWrapper : AbstractMessage { private AbstractMessage _abstractMessage; /**//// <summary> /// 构造函数 /// </summary> /// <param name="abstractMessage">AbstractMessage</param> public AbstractMessageWrapper(AbstractMessage abstractMessage) { this._abstractMessage = abstractMessage; } /**//// <summary> /// 获取Message /// </summary> /// <returns></returns> public override List<MessageModel> Get() { return _abstractMessage.Get(); } /**//// <summary> /// 插入Message /// </summary> /// <param name="mm">Message实体对象</param> /// <returns></returns> public override bool Insert(MessageModel mm) { return _abstractMessage.Insert(mm); } }} using System; using System.Collections.Generic; using System.Text; namespace Pattern.Decorator { /**//// <summary> /// 扩展出用户验证的功能（ConcreteDecorator） /// </summary> public class CheckUserWrapper : AbstractMessageWrapper { /**//// <summary> /// 构造函数 /// </summary> /// <param name="abstractMessage">AbstractMessage</param> public CheckUserWrapper(AbstractMessage abstractMessage) : base(abstractMessage) { } /**//// <summary> /// 获取Message /// </summary> /// <returns></returns> public override List<MessageModel> Get() { List<MessageModel> l = base.Get(); foreach (MessageModel mm in l) { mm.Message += "（经过用户验证）"; } return l; } /**//// <summary> /// 插入Message /// </summary> /// <param name="mm">Message实体对象</param> /// <returns></returns> public override bool Insert(MessageModel mm) { // 在这里扩展功能 return base.Insert(mm); } }} using System; using System.Collections.Generic; using System.Text; namespace Pattern.Decorator { /**//// <summary> /// 扩展出输入验证的功能（ConcreteDecorator） /// </summary> public class CheckInputWrapper : AbstractMessageWrapper { /**//// <summary> /// 构造函数 /// </summary> /// <param name="abstractMessage">AbstractMessage</param> public CheckInputWrapper(AbstractMessage abstractMessage) : base(abstractMessage) { } /**//// <summary> /// 获取Message /// </summary> /// <returns></returns> public override List<MessageModel> Get() { List<MessageModel> l = base.Get(); foreach (MessageModel mm in l) { mm.Message += "（经过输入验证）"; } return l; } /**//// <summary> /// 插入Message /// </summary> /// <param name="mm">Message实体对象</param> /// <returns></returns> public override bool Insert(MessageModel mm) { // 在这里扩展功能 return base.Insert(mm); } }} using System; using System.Data; using System.Configuration; using System.Collections; using System.Web; using System.Web.Security; using System.Web.UI; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using System.Web.UI.HtmlControls; using Pattern.Decorator; public partial class Decorator : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { AbstractMessage message = new SqlMessage(); AbstractMessageWrapper amr = new CheckUserWrapper(message); Response.Write(amr.Get()[0].Message + " " + amr.Get()[0].PublishTime.ToString()); Response.Write("<br />"); AbstractMessageWrapper amr2 = new CheckInputWrapper(message); Response.Write(amr2.Get()[0].Message + " " + amr2.Get()[0].PublishTime.ToString()); Response.Write("<br />"); AbstractMessageWrapper amr3 = new CheckUserWrapper(message); AbstractMessageWrapper amr4 = new CheckInputWrapper(amr3); Response.Write(amr4.Get()[0].Message + " " + amr4.Get()[0].PublishTime.ToString()); Response.Write("<br />"); }}