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

The ArrayList class in C# provides an indexer property that allows you to get or set elements at a specified index using square bracket notation. This property provides direct access to elements by their position in the collection.

Syntax

Following is the syntax for accessing elements by index in ArrayList −

// Get element at index
object element = arrayList[index];

// Set element at index
arrayList[index] = value;

Parameters

• index − The zero-based index of the element to get or set.

• value − The object to store at the specified index when setting.

Return Value

The indexer returns an object representing the element at the specified index. When setting, it stores the provided value at that position.

Getting Elements from ArrayList

Example

using System;
using System.Collections;

public class Demo {
    public static void Main() {
        ArrayList arrList = new ArrayList();
        arrList.Add("Laptop");
        arrList.Add("Desktop");
        arrList.Add("Notebook");
        arrList.Add("Ultrabook");
        arrList.Add("Tablet");
        arrList.Add("Headphone");
        arrList.Add("Speaker");
        
        Console.WriteLine("Elements in ArrayList...");
        foreach(string str in arrList) {
            Console.WriteLine(str);
        }
        
        Console.WriteLine("Element at index 5 = " + arrList[5]);
        Console.WriteLine("Element at index 0 = " + arrList[0]);
        Console.WriteLine("Element at index 3 = " + arrList[3]);
    }
}

The output of the above code is −

Elements in ArrayList...
Laptop
Desktop
Notebook
Ultrabook
Tablet
Headphone
Speaker
Element at index 5 = Headphone
Element at index 0 = Laptop
Element at index 3 = Ultrabook

Setting Elements in ArrayList

Example

using System;
using System.Collections;

public class Demo {
    public static void Main() {
        ArrayList arrList = new ArrayList();
        arrList.Add("Laptop");
        arrList.Add("Desktop");
        arrList.Add("Notebook");
        arrList.Add("Ultrabook");
        arrList.Add("Tablet");
        arrList.Add("Headphone");
        arrList.Add("Speaker");
        
        Console.WriteLine("Original ArrayList...");
        foreach(string str in arrList) {
            Console.WriteLine(str);
        }
        
        Console.WriteLine("Element at index 5 = " + arrList[5]);
        
        // Set new value at index 5
        arrList[5] = "SSD";
        arrList[2] = "Gaming Laptop";
        
        Console.WriteLine("\nUpdated ArrayList...");
        foreach(string str in arrList) {
            Console.WriteLine(str);
        }
        
        Console.WriteLine("Element at index 5 (Updated) = " + arrList[5]);
        Console.WriteLine("Element at index 2 (Updated) = " + arrList[2]);
    }
}

The output of the above code is −

Original ArrayList...
Laptop
Desktop
Notebook
Ultrabook
Tablet
Headphone
Speaker
Element at index 5 = Headphone

Updated ArrayList...
Laptop
Desktop
Gaming Laptop
Ultrabook
Tablet
SSD
Speaker
Element at index 5 (Updated) = SSD
Element at index 2 (Updated) = Gaming Laptop

Key Points

• ArrayList uses zero-based indexing, where the first element is at index 0.

• Accessing an invalid index throws an ArgumentOutOfRangeException.

• The indexer returns object type, so casting may be required for specific types.

• Setting an element at an index replaces the existing value at that position.

Conclusion

The ArrayList indexer provides convenient access to elements using square bracket notation. You can both retrieve and modify elements at specific positions, making it easy to work with ArrayList collections when you know the index of the elements you need to access.