CSharp - Type Creation indexer Implementation

  1. HOME
  2. CSharp
  3. Type Creation
  4. indexer Implementation

Introduction

To write an indexer, define a property called this and then set the arguments in square brackets. 

class WordList{
       string[] words = "this is a test from book2s.com".Split();

       public string this [int wordNum]      // indexer
       {
         get { return words [wordNum];  }
         set { words [wordNum] = value; }
       }
}

Here's how we could use this indexer: 

WordList s = new WordList();
Console.WriteLine (s[3]);       
s[3] = "abc";
Console.WriteLine (s[3]);

A type may declare multiple indexers, each with parameters of different types.

An indexer can also take more than one parameter: 

public string this [int arg1, string arg2]
{
       get { ... }  set { ... }
}

Omitting the set accessor makes an indexer read-only.

You can use expression-bodied syntax in indexer. 

public string this [int wordNum] => words [wordNum];

Demo

using System;
class MainClass//from ww w  . j  av  a  2s.  c  om
{
   public static void Main(string[] args)
   {
        WordList s = new WordList();
        Console.WriteLine (s[3]);       
        s[3] = "abc";
        Console.WriteLine (s[3]); 
   }
}
class WordList{
       string[] words = "this is a test from book2s.com".Split();

       public string this [int wordNum]      // indexer
       {
         get { return words [wordNum];  }
         set { words [wordNum] = value; }
       }
}

Result

Related Topics