Indexers in C# and VB.net

What are Indexers?

Indexers allow instances of a class or struct to be indexed just like arrays. Indexers resemble properties except that their accessors take parameters.

  • A class can have only one Indexer
  • In VB.net, default keyword is required to make it indexer
  • Index can be accessed either by a numeric index or even string

How to Use (C#)?

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace CSconsole

{

class NamesList

{

public int Length

{

get { return objList.Count; }

}

List<String> objList = new List<string>();

public string this[int index]

{

get { return objList[index]; }

set { objList.Add (value); }

}

}

public class TestIndexers

{

public static void Main()

{

NamesList obj = new NamesList();

obj[0] = "UserA";

obj[1] = "UserB";

for(int i=0;i

{

Console.WriteLine(obj[i]);

}

Console.ReadKey();

}

}

}

How to Use (VB.net)?

Imports System.Collections.Generic

Public Class NamesList

Dim Names As New List(Of String)

Default Public Property LastName(ByVal index As Integer) As String

Get

Return Names(index)

End Get

Set(ByVal value As String)

Names.Add(value)

End Set

End Property

Public Property FirstName(ByVal index As Integer) As String

Get

Return Names(index)

End Get

Set(ByVal value As String)

Names.Add(value)

End Set

End Property

Public Shared Sub Main()

Dim obj As New NamesList()

obj(0) = "User1"

Console.WriteLine(obj(0))

Console.Read()

End Sub

End Class

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