ex-09-10

Programming Csharp Source Code(代码) Programming Csharp Source Code

// Example 09-10: Overloading an index

namespace Programming_CSharp
{
   using System;
  
   // a simplified ListBox control
   public class ListBoxTest
   {
      // initialize the list box with strings
      public ListBoxTest(params string[] initialStrings)
      {
         // allocate space for the strings
         strings = new String[256]; 

         // copy the strings passed in to the constructor
         foreach (string s in initialStrings)
         {
            strings[ctr++] = s;
         }
      }

      // add a single string to the end of the list box
      public void Add(string theString)
      {
         strings[ctr] = theString;
         ctr++;
      }

      // allow array-like access
      public string this[int index]
      {
         get
         {
            if (index < 0 || index >= strings.Length)
            {
               // handle bad index
            }
            return strings[index];
         }
         set
         {
            strings[index] = value;
         }
      }
   
      private int findString(string searchString)
      {
         for (int i = 0;i<strings.Length;i++)
         {
            if (strings[i].StartsWith(searchString))
            {
               return i;
            }
         }
         return -1;
      }
      // index on string
      public string this[string index]
      {
         get
         {
            if (index.Length == 0)
            {
               // handle bad index
            }

            return this[findString(index)];
         }
         set
         {
            strings[findString(index)] = value;
         }
      }


      // publish how many strings you hold
      public int GetNumEntries()
      {
         return ctr;
      }

      private string[] strings;
      private int ctr = 0;
   }

   public class Tester
   {        
      static void Main()
      {
         // create a new list box and initialize
         ListBoxTest lbt = 
            new ListBoxTest("Hello", "World");

         // add a few strings
         lbt.Add("Who");
         lbt.Add("Is");
         lbt.Add("John");
         lbt.Add("Galt");

         // test the access
         string subst = "Universe";
         lbt[1] = subst;
         lbt["Hel"] = "GoodBye";
         // lbt["xyz"] = "oops";

         // access all the strings
         for (int i = 0;i<lbt.GetNumEntries();i++)
         {
            Console.WriteLine("lbt[{0}]: {1}",i,lbt[i]);
         }      // end for
      }         // end main
   }            // end tester
}               // end namespace