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Resources » Articles » .NET Framework

What are Indexers

Posted Date: 01-Sep-2004	Category: .NET Framework	Rating:
Author: G.B Naveen Kumar	Member Level: Bronze	Points: 5

This article explains Indexers in C#

Defining an indexer allows you to create classes that act like "virtual arrays." Instances of that class can be accessed using the [] array access operator. Defining an indexer in C# is similar to defining operator [] in C++, but is considerably more flexible. For classes that encapsulate array- or collection-like functionality, using an indexer allows the users of that class to use the array syntax to access the class.

Example

The following example shows how to declare a private array field, myArray, and an indexer. Using the indexer allows direct access to the instance b[i]. The alternative to using the indexer is to declare the array as a public member and access its members, myArray[i], directly.

// cs_keyword_indexers.cs
using System;
class IndexerClass
{
private int [] myArray = new int[100];
public int this [int index] // Indexer declaration
{
get
{
// Check the index limits.
if (index < 0 || index >= 100)
return 0;
else
return myArray[index];
}
set
{
if (!(index < 0 || index >= 100))
myArray[index] = value;
}
}
}

public class MainClass
{
public static void Main()
{
IndexerClass b = new IndexerClass();
// Call the indexer to initialize the elements #3 and #5.
b[3] = 256;
b[5] = 1024;
for (int i=0; i<=10; i++)
{
Console.WriteLine("Element #{0} = {1}", i, b[i]);
}
}
}

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Responses to "What are Indexers"

Author: desifella 03 Sep 2004

Member Level: Bronze Points : 0

Hi Naveen,
Even though the article helped me to recollect what indexers are it doesn't deal with all the info related to indexers(like what are the restrictions on having multiple indexers and why is it a good thing and a real world scenario). It will be nice if you try to make this as comprehensible as possible. Good effort though.
-desi

Author: Kamran 20 Apr 2005

Member Level: Bronze Points : 0

can i use indexers in .net frame work 1.1?? & can we use this approach in vb.net?

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