Define indexer : Indexer : Class Interface C# Source Code

    

/*
Learning C# 
by Jesse Liberty

Publisher: O'Reilly 
ISBN: 0596003765
*/
 using System;

 namespace Indexers
 {
     // a simplified ListBox control
     class ListBoxTest
     {
         private string[] strings;
         private int ctr = 0;

         // initialize the listbox 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 listbox
         public void Add(string theString)
         {
             if (ctr >= strings.Length)
             {
                 // handle bad index
             }
             else
                 strings[ctr++] = theString;
         }

         // allow array-like access
         public string this[int index]
         {
             get
             {
                 if (index < 0 || index >= strings.Length)
                 {
                     // handle bad index
                 }
                 return strings[index];
             }
             set
             {
                 // add only through the add method
                 if (index >= ctr )
                 {
                     // handle error
                 }
                 else
                     strings[index] = value;
             }
         }

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

     }

    public class TesterListBoxTest
    {
       [STAThread]
       static void Main()
       {
           // create a new listbox and initialize
           ListBoxTest lbt =
               new ListBoxTest("Hello", "World");

           Console.WriteLine("After creation...");
           for (int i = 0;i<lbt.GetNumEntries();i++)
           {
               Console.WriteLine("lbt[{0}]: {1}",i,lbt[i]);
           }

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

           Console.WriteLine("\nAfter adding strings...");
           for (int i = 0;i<lbt.GetNumEntries();i++)
           {
               Console.WriteLine("lbt[{0}]: {1}",i,lbt[i]);
           }


           // test the access
           string subst = "Universe";
           lbt[1] = subst;

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