CSharp: Chain of Responsibility Pattern

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/// <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);      }  }

　　

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/// <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);          }        }  }

　　

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/// <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;      }  }

　　

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/// <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);              }          }      }  }

　　

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/// <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);              }          }        }  }

　　

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/// <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：

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/// <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);      }  }

　　

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