C# | Check if the ArrayList has a fixed size

Last Updated : 11 Jul, 2025

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.IsFixedSize property is used to check whether the ArrayList has a fixed size or not. Properties:

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 bool IsFixedSize { get; }

Return Value: This method returns True if the ArrayList has a fixed size, otherwise returns False. The default value is False. Below programs illustrate the use of ArrayList.IsFixedSize Property: Example 1:

CSHARP

// C# code to check if the ArrayList
// has fixed size or not
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
        myList.Add("A");
        myList.Add("B");
        myList.Add("C");
        myList.Add("D");
        myList.Add("E");
        myList.Add("F");

        // To check if the ArrayList has fixed size or not
        Console.WriteLine(myList.IsFixedSize);
    }
}

Output:

False

Example 2:

CSharp

// C# code to check if the ArrayList 
// has fixed size or not 
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 
        myList.Add("1"); 
        myList.Add("2"); 
        myList.Add("3"); 
        myList.Add("4"); 
        myList.Add("5"); 
        myList.Add("6"); 

        // To check if the ArrayList 
        // has fixed size or not
        // it will return false
        Console.WriteLine(myList.IsFixedSize); 
      
      
        // Create a fixed-size wrapper
        // around the ArrayList
        ArrayList myListfixed = ArrayList.FixedSize(myList);

        // To check if the ArrayList
        // has fixed size or not
        // it will return true
        Console.WriteLine(myListfixed.IsFixedSize); 
      
      
    } 
}

Output:

False
True

Note:

A collection with a fixed size does not allow the addition or removal of elements after the collection is created, but it allows the modification of existing elements.
Retrieving the value of this property is an O(1) operation.

Reference:

https://learn.microsoft.com/en-us/dotnet/api/system.collections.arraylist.isfixedsize?view=netframework-4.7.2

Introduction to .NET Framework

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C# | Check if the ArrayList has a fixed size

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