C# | Indexers

Prerequisite: Properties in C#

An indexer allows an instance of a class or struct to be indexed as an array. If the user will define an indexer for a class, then the class will behave like a virtual array. Array access operator i.e ([ ]) is used to access the instance of the class which uses an indexer. A user can retrieve or set the indexed value without pointing an instance or a type member. Indexers are almost similar to the Properties. The main difference between Indexers and Properties is that the accessors of the Indexers will take parameters.


[access_modifier] [return_type] this [argument_list]
     // get block code
    // set block code


In the above syntax:

  • access_modifier: It can be public, private, protected or internal.
  • return_type: It can be any valid C# type.
  • this: It is the keyword which points to the object of the current class.
  • argument_list: This specifies the parameter list of the indexer.
  • get{ } and set { }: These are the accessors.






// C# program to illustrate the Indexer
using System;
// class declaration
class IndexerCreation 
    // class members
    private string[] val = new string[3]; 
    // Indexer declaration
    // Here pubic is the modifier
    // string is the return type of 
    // Indexer and "this" is the keyword
    // having parameters list
    public string this[int index] 
        // get Accessor
        // retrieving the values 
        // stored in val[] array
        // of strings
            return val[index];
        // set Accessor
        // setting the value at 
        // passed index of val
            // value keyword is used
            // to define the value 
            // being assigned by the
            // set indexer. 
            val[index] = value;
// Driver Class
class main {
    // Main Method
    public static void Main() {
        // creating an object of parent class which
        // acts as primary address for using Indexer
        IndexerCreation ic = new IndexerCreation();
        // Inserting values in ic[]
        // Here we are using the object
        // of class as an array
        ic[0] = "C";
        ic[1] = "CPP";
        ic[2] = "CSHARP";
        Console.Write("Printing values stored in objects used as arrays\n");
        // printing values 
        Console.WriteLine("First value = {0}", ic[0]);
        Console.WriteLine("Second value = {0}", ic[1]);
        Console.WriteLine("Third value = {0}", ic[2]);



Printing values stored in objects used as arrays
First value = C
Second value = CPP
Third value = CSHARP

Important Points About Indexers:

  • There are two types of Indexers i.e. One Dimensional Indexer & MultiDimensional Indexer. The above discussed is One Dimensional Indexer.
  • Indexers can be overloaded.
  • These are different from Properties.
  • This enables the object to be indexed in a similar way to arrays.
  • A set accessor will always assign the value while the get accessor will return the value.
  • this” keyword is always used to declare an indexer.
  • To define the value being assigned by the set indexer, ” value” keyword is used.
  • Indexers are also known as the Smart Arrays or Parameterized Property in C#.
  • Indexer can’t be a static member as it is an instance member of the class.

My Personal Notes arrow_drop_up

Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.

Article Tags :


Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.