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C# | Check if the ArrayList is read-only

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  • Last Updated : 01 Feb, 2019
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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.IsReadOnly property is used to check whether the ArrayList is read-only or not.


  • 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.


public virtual bool IsReadOnly { get; }

Return Value: This method returns True if the ArrayList is read-only, otherwise returns False. The default value is False.


// C# code to check if the ArrayList
// is read-only 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("Geeks Classes");
        // To check if the ArrayList is read-only or not




  • A collection that is read-only does not allow the addition, removal, or modification of elements after the collection is created.
  • Retrieving the value of this property is an O(1) operation.


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