How to create the ArrayList in C# Last Updated : 11 Jul, 2025 Comments Improve Suggest changes Like Article Like Report ArrayList() constructor is used to initialize a new instance of the ArrayList class which will be empty and will have the default initial capacity. 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. Syntax: public ArrayList (); Important Points: The number of elements that an ArrayList can hold is known as the Capacity of the ArrayList. If the elements will be added to the ArrayList then capacity will be automatically increased by reallocating the internal array. Specifying the initial capacity will eliminate the requirement to perform a number of resizing operations while adding elements to the ArrayList if the size of the collection can be estimated. This constructor is an O(1) operation. Example 1: csharp // C# Program to illustrate how // to create a ArrayList using System; using System.Collections; class Geeks { // Main Method public static void Main(String[] args) { // arrlist is the ArrayList object // ArrayList() is the constructor // used to initializes a new // instance of the ArrayList class ArrayList arrlist = new ArrayList(); // Count property is used to get the // number of elements in ArrayList // It will give 0 as no elements // are present currently Console.WriteLine(arrlist.Count); } } Output: 0 Example 2: csharp // C# Program to illustrate how // to create a ArrayList using System; using System.Collections; class Geeks { // Main Method public static void Main(String[] args) { // arrlist is the ArrayList object // ArrayList() is the constructor // used to initializes a new // instance of the ArrayList class ArrayList arrlist = new ArrayList(); Console.Write("Before Add Method: "); // Count property is used to get the // number of elements in ArrayList // It will give 0 as no elements // are present currently Console.WriteLine(arrlist.Count); // Adding the elements // to the ArrayList arrlist.Add("This"); arrlist.Add("is"); arrlist.Add("C#"); arrlist.Add("ArrayList"); Console.Write("After Add Method: "); // Count property is used to get the // number of elements in arrlist Console.WriteLine(arrlist.Count); } } Output: Before Add Method: 0 After Add Method: 4 Reference: https://learn.microsoft.com/en-us/dotnet/api/system.collections.arraylist.-ctor?view=netframework-4.7.2#System_Collections_ArrayList__ctor Comment More infoAdvertise with us K Kirti_Mangal Follow Improve Article Tags : C# CSharp-Collections-Namespace CSharp-Collections-ArrayList 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