C# | Get the number of elements actually contained in the ArrayList

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.Count property gets the number of elements actually contained in the ArrayList.

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 int Count { get; }

Return Value: The number of elements actually contained in the ArrayList.

Below given are some examples to understand the implementation in a better way:

Example 1:

// C# code to get the number of elements
// actually contained in the ArrayList
using System;
using System.Collections;
using System.Collections.Generic;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating an ArrayList
        ArrayList myList = new ArrayList();

        // Displaying the number of elements in ArrayList
        Console.WriteLine("Number of elements : " + myList.Count);

        // Adding elements to ArrayList
        myList.Add(1);
        myList.Add(2);
        myList.Add(3);
        myList.Add(4);
        myList.Add(5);

        // Displaying the number of elements in ArrayList
        Console.WriteLine("Number of elements : " + myList.Count);
    }
}

Output:

Number of elements : 0
Number of elements : 5

Example 2:

// C# code to get the number of elements
// actually contained in the ArrayList
using System;
using System.Collections;
using System.Collections.Generic;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating an ArrayList
        ArrayList myList = new ArrayList();

        // Displaying the number of elements in ArrayList
        Console.WriteLine("Number of elements : " + myList.Count);

        // Adding elements to ArrayList
        myList.Add("First");
        myList.Add("Second");
        myList.Add("Third");
        myList.Add("Fourth");
        myList.Add("Fifth");
        myList.Add("Sixth");
        myList.Add("Seventh");
        myList.Add("Eighth");

        // Displaying the number of elements in ArrayList
        Console.WriteLine("Number of elements : " + myList.Count);
    }
}

Output:

Number of elements : 0
Number of elements : 8

Note:

• Capacity is the number of elements that the ArrayList can store. The count is the number of elements that are actually in the ArrayList.
• Capacity is always greater than or equal to Count. If Count exceeds Capacity while adding elements, the capacity is automatically increased by reallocating the internal array before copying the old elements and adding the new elements.
• Retrieving the value of this property is an O(1) operation.

Reference:

• https://docs.microsoft.com/en-us/dotnet/api/system.collections.arraylist.count?view=netframework-4.7.2