INTERVIEW QUESTIONS MICROSOFT C# DETAILS

Question: What is indexer? where it is used plz explain

Answer: Indexer is a special syntax for overloading [] operator for a class. After defining an indexer, array syntaxes can be used for the class objects.

Indexer is a special syntax for overloading [] operator for a class. After defining an indexer, array syntaxes can be used for the class objects.
Source: CoolInterview.com

Indexer is usually used to traverse arrays. We can transfer this sort of functionality to our classes.

When creating a class of lets say Person

public class Person
{
private string name;

// create fields to hide the functionality
Public string Name
{
get{return name;}
set{name = value;}
}
// if we use this class the only one person name at a time will be saved at a time.

In order to keep a list of names we use an indexer which is used by the System.Collections namespace
iEnumberable; Icollection; IList; IDictionary

public class Persons :CollectionBase
{
public Person this[int personIndex] // indexer
{
get{return (Person)List[personIndex];}
set{List[personIndex]=value;}
}
}
Here we are using the IList.List property in the ArrayList of the CollectionBase

Of Course to add members to the list we must also add functionality by way of methods that the List.Add() and List.Remove()
portions of the class

Let me continue the Add functionality for you and I am sure that you can figure out the rest.

Public void Add(Person newPerson)
{
List.Add(newPerson); // adds the person to the list that will be accessed by the indexer
} Source: CoolInterview.com

An indexer is a member that enables an object to be indexed in the same way as an array. Source: CoolInterview.com

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