Decorator 在程序运行时生成新的操作,这些新的操作是原有的操作的变体

ISimpleWriter
 1using System;
 2using System.Collections.Generic;
 3using System.Text;
 4
 5namespace Gof.Nan.Test.Decorator
 6{
 7    public interface ISimpleWriter
 8    {
 9        void Write(char c);
10        void Write(string s);
11        void WriteLine();
12        void Close();
13    }
14}

SimpleStreamWriter
 1using System;
 2using System.Collections.Generic;
 3using System.Text;
 4using System.IO;
 5
 6namespace Gof.Nan.Test.Decorator
 7{
 8    public class SimpleStreamWriter : StreamWriter,ISimpleWriter
 9    {
10        public SimpleStreamWriter(Stream s)
11            : base(s)
12        { 
13        }
14
15        public SimpleStreamWriter(string path)
16            : base(path)
17        {
18        }
19    }
20}

OozinozFilter
 1using System;
 2using System.Collections.Generic;
 3using System.Text;
 4
 5namespace Gof.Nan.Test.Decorator
 6{
 7    public abstract class OozinozFilter : ISimpleWriter
 8    {
 9        protected ISimpleWriter _writer;
10
11        public OozinozFilter(ISimpleWriter w)
12        {
13            _writer = w;
14        }
15
16        ISimpleWriter 成员#region ISimpleWriter 成员
17
18        public abstract void Write(char c);
19
20        public virtual void Write(string s)
21        {
22            foreach (char c in s.ToCharArray())
23            {
24                Write(c);
25            }
26        }
27
28        public virtual void WriteLine()
29        {
30            _writer.WriteLine();
31        }
32
33        public void Close()
34        {
35            _writer.Close();
36        }
37
38        #endregion
39    }
40}

LowerCaseFilter
 1using System;
 2using System.Collections.Generic;
 3using System.Text;
 4
 5namespace Gof.Nan.Test.Decorator
 6{
 7    public class LowerCaseFilter : OozinozFilter
 8    {
 9        public LowerCaseFilter(ISimpleWriter w)
10            : base(w)
11        {
12        }
13
14        public override void Write(char c)
15        {
16            _writer.Write(char.ToLower(c));
17        }
18    }
19}
20

客户代码
 1using System;
 2using System.Collections.Generic;
 3using System.Text;
 4
 5namespace Gof.Nan.Test.Decorator
 6{
 7    public class ShowLowerCase
 8    {
 9        static void Main(string[] args)
10        {
11            ISimpleWriter w = new SimpleStreamWriter("sample.txt");
12            ISimpleWriter x = new LowerCaseFilter(w);
13            x.Write("This Text,notably ALL in LoweR CasE!");
14            x.Close();
15        }
16    }
17}

类图：
 
The Decorator Pattern attaches additional responsibilities to an object dynamically. Decorators provide a flexible alternative to subclassing for extending functionality.