C# | Get or set the element at the specified index in ArrayList

Last Updated : 20 Jun, 2022

ArrayList.Item[Int32] Property is used to get or set the element at the specified index in ArrayList. Syntax:

public virtual object this[int index] { get; set; }

Here, index is the zero-based index of the element to get or set. Return Value: It returns the element of Object type at the specified index. Exception: This property will throw ArgumentOutOfRangeException if the index is less than zero or is equal to or greater than Count. Below programs illustrate the use of above-discussed property: Example 1:

CSharp

// C# code to get or set the element at 
// the specified index in ArrayList 
using System; 
using System.Collections; 

class GFG { 

    // Driver code 
    public static void Main() 
    { 

        // Creating an ArrayList 
        ArrayList myList = new ArrayList(); 

        // Adding elements to ArrayList 
        myList.Add("A"); 
        myList.Add("B"); 
        myList.Add("C"); 
        myList.Add("D"); 
        myList.Add("E"); 
        myList.Add("F"); 

        // Displaying the elements 
        // in the ArrayList 
        foreach(string str in myList) 
        { 
            Console.WriteLine(str); 
        } 

        Console.WriteLine("After Item[int32] Property: "); 

        // setting the value at index 2 
        myList[2] = "Z"; 

        // Displaying the elements 
        // in the ArrayList 
        foreach(string str in myList) 
        { 
            Console.WriteLine(str); 
        } 
    } 
}

Output:

A
B
C
D
E
F
After Item[int32] Property: 
A
B
Z
D
E
F

Example 2:

CSharp

// C# code to get or set the element at 
// the specified index in ArrayList 
using System; 
using System.Collections; 
using System.Collections.Generic; 

class GFG { 

    // Driver code 
    public static void Main() 
    { 

        // Creating an ArrayList 
        ArrayList myList = new ArrayList(); 

        // Adding elements to ArrayList 
        // Adding elements to ArrayList 
        myList.Add(2); 
        myList.Add(4); 
        myList.Add(6); 
        myList.Add(8); 
        myList.Add(10); 
        myList.Add(12); 
        myList.Add(14); 
        myList.Add(16); 
        myList.Add(18); 
        myList.Add(20); 

        // Displaying the elements 
        // in the ArrayList 
        foreach(int i in myList) 
        { 
            Console.WriteLine(i); 
        } 

        Console.WriteLine("After Item[int32] Property: "); 

        // setting the value at index 8 
        // this will give error as index 
        // is greater than count 
        myList[10] = 56; 

        // Displaying the elements 
        // in the ArrayList 
        foreach(int j in myList) 
        { 
            Console.WriteLine(j); 
        } 
    } 
}

Runtime Error:

Unhandled Exception: System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index

Time complexity: O(n) for traversing ArrayList

Auxiliary Space: O(n) where n is the size of the ArrayList

Reference: