C#使用委托

using System;
using System.IO;

namespace DelegateAppl {

   class PrintString {
      static fileStream fs;
      static StreamWriter sw;

      // delegate declaration
      public delegate voID printString(string s);

      // this method prints to the console
      public static voID WritetoScreen(string str) {
         Console.Writeline("The String is: {0}", str);
      }

      //this method prints to a file
      public static voID Writetofile(string s) {
         fs = new fileStream("c:\message.txt",
         fileMode.Append, fileAccess.Write);
         sw = new StreamWriter(fs);
         sw.Writeline(s);
         sw.Flush();
         sw.Close();
         fs.Close();
      }

      // this method takes the delegate as parameter and uses it to
      // call the methods as required
      public static voID sendString(printString ps) {
         ps("Hello World");
      }

      static voID Main(string[] args) {
         printString ps1 = new printString(WritetoScreen);
         printString ps2 = new printString(Writetofile);
         sendString(ps1);
         sendString(ps2);
         Console.ReadKey();
      }
   }
}