CSharp: Chain of Responsibility Pattern

   /// <summary>
    /// Chain of Responsibility  Patterns 责任链模式 
    /// 20220918
    /// geovindu,Geovin Du,涂聚文
    /// </summary>
    public abstract class Chain
    {
        /// <summary>
        /// describes how all chains work
        /// </summary>
        private bool hasLink;
        protected Chain chn;
        public Chain()
        {
            hasLink = false;
        }
        /// <summary>
        /// you must implement this in derived classes
        /// </summary>
        /// <param name="mesg"></param>
        public abstract void sendToChain(string mesg);
        /// <summary>
        /// 
        /// </summary>
        /// <param name="c"></param>
        public void addToChain(Chain c)
        {
            //add new element to chain
            chn = c;
            hasLink = true;		//flag existence
        }
        /// <summary>
        /// 
        /// </summary>
        /// <returns></returns>
        public Chain getChain()
        {
            return chn;	//get the chain link
        }
        /// <summary>
        /// 
        /// </summary>
        /// <returns></returns>
        public bool hasChain()
        {
            return hasLink;		//true if linked to another
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="mesg"></param>
        protected void sendChain(string mesg)
        {
            //send message on down the chain
            if (chn != null)
                chn.sendToChain(mesg);
        }
    }

　　

   /// <summary>
    /// receives color names in chain
    /// Chain of Responsibility  Patterns 责任链模式 
    /// 20220918
    /// geovindu,Geovin Du,涂聚文
    /// </summary>
    public class ColorChain : Chain
    {
        private Hashtable colHash;	//color list kept here
        private Panel panel;		//color goes here
        /// <summary>
        /// 
        /// </summary>
        /// <param name="pnl"></param>
        public ColorChain(Panel pnl)
        {
            panel = pnl;			//save reference
            //create Hash table to correlate color names
            //with actual Color objects
            colHash = new Hashtable();
            colHash.Add("red", Color.Red);
            colHash.Add("green", Color.Green);
            colHash.Add("blue", Color.Blue);
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="mesg"></param>
        public override void sendToChain(string mesg)
        {
            mesg = mesg.ToLower();
            try
            {
                Color c = (Color)colHash[mesg];
                //if this is a color, put it in the panel
                panel.BackColor = c;
            }
            catch (NullReferenceException e)
            {
                //send on if this doesn't work
                sendChain(mesg);
            }

        }
    }

　　

   /// <summary>
    /// A simple file handlng class
    /// Chain of Responsibility  Patterns 责任链模式 
    /// 20220918
    /// geovindu,Geovin Du,涂聚文
    /// </summary>
    public class csFile
    {
        private string fileName;
        StreamReader ts;
        StreamWriter ws;
        private bool opened, writeOpened;
        /// <summary>
        /// 
        /// </summary>
        public csFile()
        {
            init();
        }
        /// <summary>
        /// 
        /// </summary>
        private void init()
        {
            opened = false;
            writeOpened = false;
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="file_name"></param>
        public csFile(string file_name)
        {
            fileName = file_name;
            init();
        }
        /// <summary>
        /// 
        /// </summary>
        /// <returns></returns>
        public bool exists()
        {
            return File.Exists(fileName);
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="file_name"></param>
        /// <returns></returns>
        public bool OpenForRead(string file_name)
        {
            fileName = file_name;
            try
            {
                ts = new StreamReader(fileName);
                opened = true;
            }
            catch (FileNotFoundException)
            {
                return false;
            }
            return true;
        }
        /// <summary>
        /// 
        /// </summary>
        /// <returns></returns>
        public bool OpenForRead()
        {
            return OpenForRead(fileName);
        }
        /// <summary>
        /// 
        /// </summary>
        /// <returns></returns>
        public string readLine()
        {
            return ts.ReadLine();
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="s"></param>
        public void writeLine(string s)
        {
            ws.WriteLine(s);
        }
        /// <summary>
        /// 
        /// </summary>
        public void close()
        {
            if (opened)
                ts.Close();
            if (writeOpened)
                ws.Close();
        }
        /// <summary>
        /// 
        /// </summary>
        /// <returns></returns>
        public bool OpenForWrite()
        {
            return OpenForWrite(fileName);
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="file_name"></param>
        /// <returns></returns>
        public bool OpenForWrite(string file_name)
        {
            try
            {
                ws = new StreamWriter(file_name);
                fileName = file_name;
                writeOpened = true;
                return true;
            }
            catch (FileNotFoundException)
            {
                return false;
            }
        }
        /// <summary>
        /// 
        /// </summary>
        /// <returns></returns>
        public string getRootName()
        {
            int i = fileName.LastIndexOf("\\");
            string root = fileName;
            if (i > 0)
            {
                root = fileName.Substring(i + 1);
            }
            return root;
        }
    }

　　

   /// <summary>
    /// Summary description for FileChain.
    /// Chain of Responsibility  Patterns 责任链模式 
    /// 20220918
    /// geovindu,Geovin Du,涂聚文
    /// </summary>
    public class FileChain : Chain
    {
        ListBox flist;
        /// <summary>
        /// 
        /// </summary>
        /// <param name="lb"></param>
        public FileChain(ListBox lb)
        {
            flist = lb;
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="mesg"></param>
        public override void sendToChain(string mesg)
        {
            //if the string matches any part of a filename
            //put those filenames in the file list box
            string[] files;
            string fname = mesg + "*.*";
            files = Directory.GetFiles(Directory.GetCurrentDirectory(), fname);
            //add them all to the listbox
            if (files.Length > 0)
            {
                for (int i = 0; i < files.Length; i++)
                {
                    csFile vbf = new csFile(files[i]);
                    flist.Items.Add(vbf.getRootName());
                }
            }
            else
            {
                if (hasChain())
                {
                    chn.sendToChain(mesg);
                }
            }
        }
    }

　　

   /// <summary>
    /// Summary description for ImageChain.
    /// Chain of Responsibility  Patterns 责任链模式 
    /// 20220918
    /// geovindu,Geovin Du,涂聚文
    /// </summary>
    public class ImageChain : Chain
    {
        PictureBox picBox;		//image goes here
        /// <summary>
        /// 
        /// </summary>
        /// <param name="pc"></param>
        public ImageChain(PictureBox pc)
        {
            picBox = pc;		//save reference
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="mesg"></param>
        public override void sendToChain(string mesg)
        {
            //put image in picture box
            string fname = mesg + ".jpg";	//assume jpg filename
            csFile fl = new csFile(fname);
            if (fl.exists())
                picBox.Image = new Bitmap(fname);
            else
            {
                if (hasChain())
                {	//send off down chain
                    chn.sendToChain(mesg);
                }
            }

        }
    }

　　

   /// <summary>
    /// handles command that is not otherwise legal
    /// Chain of Responsibility  Patterns 责任链模式 
    /// 20220918
    /// geovindu,Geovin Du,涂聚文
    /// </summary>
    public class NoCmd : Chain
    {

        /// <summary>
        /// 
        /// </summary>
        private ListBox lsNocmd;	//commands go here
        /// <summary>
        /// 
        /// </summary>
        /// <param name="lb"></param>
        public NoCmd(ListBox lb)
        {
            lsNocmd = lb;			//copy reference
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="mesg"></param>
        public override void sendToChain(string mesg)
        {
            //adds unknown commands to list box
            lsNocmd.Items.Add(mesg);
        }
    }

　　

调用：

   /// <summary>
    /// Chain of Responsibility  Patterns 责任链模式 
    /// 20220918
    /// geovindu,Geovin Du,涂聚文
    /// </summary>
    public partial class ChainofResponsibilityPatternsForm : Form
    {
        /// <summary>
        /// 
        /// </summary>
        private Chain chn;
        /// <summary>
        /// 
        /// </summary>
        private void init()
        {
            //set up chains
            ColorChain clrChain = new ColorChain(pnlColor);
            FileChain flChain = new FileChain(lsFiles);
            NoCmd noChain = new NoCmd(lsNocmd);
            //create chain links
            chn = new ImageChain(picImage);
            chn.addToChain(clrChain);
            clrChain.addToChain(flChain);
            flChain.addToChain(noChain);
        }
        /// <summary>
        /// 
        /// </summary>
        public ChainofResponsibilityPatternsForm()
        {
            InitializeComponent();
            init();
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void ChainofResponsibilityPatternsForm_Load(object sender, EventArgs e)
        {

        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btSend_Click(object sender, EventArgs e)
        {
            chn.sendToChain(txCommand.Text);
        }
    }

　　

输出：