C# | Insert an element into the ArrayList at the specified index Last Updated : 11 Jul, 2025 Comments Improve Suggest changes Like Article Like Report ArrayList represents an ordered collection of an object that can be indexed individually. It is basically an alternative to an array. It also allows dynamic memory allocation, adding, searching and sorting items in the list. ArrayList.Insert(Int32, Object) method inserts an element into the ArrayList at the specified index. Properties of ArrayList Class: Elements can be added or removed from the Array List collection at any point in time. The ArrayList is not guaranteed to be sorted. The capacity of an ArrayList is the number of elements the ArrayList can hold. Elements in this collection can be accessed using an integer index. Indexes in this collection are zero-based. It also allows duplicate elements. Using multidimensional arrays as elements in an ArrayList collection is not supported. Syntax : public virtual void Insert (int index, object value); Parameters: index : It is the zero-based index at which value should be inserted. value : It is the Object which is to be inserted. The value can be null. Exceptions: ArgumentOutOfRangeException : If index is less than zero or index is greater than Count i.e, number of elements in the ArrayList. NotSupportedException : If the ArrayList is read-only or the ArrayList has a fixed size. Below given are some examples to understand the implementation in a better way: Example 1: CSHARP // C# code to insert an element // into the ArrayList at the // specified index using System; using System.Collections; using System.Collections.Generic; class GFG { // Driver code public static void Main() { // Creating an ArrayList ArrayList myList = new ArrayList(10); // Adding elements to ArrayList myList.Add("A"); myList.Add("B"); myList.Add("C"); // Displaying the elements in ArrayList Console.WriteLine("The initial ArrayList is : "); foreach(string str in myList) { Console.WriteLine(str); } // Inserting 3 elements at random index in the ArrayList myList.Insert(1, "D"); myList.Insert(4, "E"); myList.Insert(5, "F"); // Displaying the modified ArrayList Console.WriteLine("The ArrayList after Inserting elements is : "); // Displaying the elements in ArrayList foreach(string str in myList) { Console.WriteLine(str); } } } Output: The initial ArrayList is : A B C The ArrayList after Inserting elements is : A D B C E F Example 2: CSHARP // C# code to insert an element // into the ArrayList at the // specified index using System; using System.Collections; using System.Collections.Generic; class GFG { // Driver code public static void Main() { // Creating an ArrayList ArrayList myList = new ArrayList(10); // Adding elements to ArrayList myList.Add(1); myList.Add(2); myList.Add(3); // Displaying the elements in ArrayList Console.WriteLine("The initial ArrayList is : "); foreach(int i in myList) { Console.WriteLine(i); } // Inserting 3 elements in front of the ArrayList myList.Insert(0, 4); myList.Insert(0, 5); myList.Insert(0, 6); // Displaying the modified ArrayList Console.WriteLine("The ArrayList after Inserting elements is : "); // Displaying the elements in ArrayList foreach(int i in myList) { Console.WriteLine(i); } } } Output: The initial ArrayList is : 1 2 3 The ArrayList after Inserting elements is : 6 5 4 1 2 3 Note: If index is equal to Count i.e, number of elements in the ArrayList, value is added to the end of ArrayList. This method is an O(n) operation, where n is Count. Reference: https://learn.microsoft.com/en-us/dotnet/api/system.collections.arraylist.insert?view=netframework-4.7.2 Comment More infoAdvertise with us S Sahil_Bansall Follow Improve Article Tags : Misc C# CSharp-method CSharp-Collections-Namespace CSharp-Collections-ArrayList +1 More Practice Tags : Misc Explore IntroductionC# Tutorial 4 min read Introduction to .NET Framework 6 min read C# .NET Framework (Basic Architecture and Component Stack) 6 min read C# Hello World 4 min read Common Language Runtime (CLR) in C# 4 min read FundamentalsC# Identifiers 2 min read C# Data Types 7 min read C# Variables 4 min read C# Literals 5 min read C# Operators 7 min read C# Keywords 5 min read Control StatementsC# Decision Making (if, if-else, if-else-if ladder, nested if, switch, nested switch) 5 min read C# Switch Statement 4 min read C# Loops 4 min read C# Jump Statements (Break, Continue, Goto, Return and Throw) 4 min read OOP ConceptsC# Class and Objects 5 min read C# Constructors 5 min read C# Inheritance 6 min read C# Encapsulation 4 min read C# Abstraction 4 min read MethodsC# Methods 4 min read C# Method Overloading 4 min read C# | Method Parameters 7 min read C# Method Overriding 9 min read Anonymous Method in C# 3 min read ArraysC# Arrays 8 min read C# Jagged Arrays 4 min read C# Array Class 7 min read How to Sort an Array in C# | Array.Sort() Method Set - 1 8 min read How to find the rank of an array in C# 2 min read ArrayListArrayList in C# 6 min read C# ArrayList Class 7 min read C# | Array vs ArrayList 2 min read StringC# Strings 7 min read C# Verbatim String Literal - @ 5 min read C# String Class 9 min read C# StringBuilder 4 min read C# String vs StringBuilder 3 min read TupleC# Tuple 7 min read C# Tuple Class 3 min read C# ValueTuple 7 min read C# ValueTuple Struct 4 min read IndexersC# Indexers 4 min read C# Multidimensional Indexers 5 min read C# - Overloading of Indexers 3 min read Like