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

The Count property in C# is used to get the number of elements actually contained in an ArrayList. This property returns an integer representing the current number of elements, which is different from the Capacity property that indicates the total storage space available.

Syntax

Following is the syntax for using the Count property −

int elementCount = arrayListName.Count;

Count vs Capacity

Using Count Property

Example

using System;
using System.Collections;

public class Demo {
    public static void Main(String[] args) {
        ArrayList list1 = new ArrayList();
        list1.Add("A");
        list1.Add("B");
        list1.Add("C");
        list1.Add("D");
        list1.Add("E");
        list1.Add("F");
        list1.Add("G");
        list1.Add("H");
        list1.Add("I");

        Console.WriteLine("Elements in ArrayList1...");
        foreach (string res in list1) {
            Console.WriteLine(res);
        }

        ArrayList list2 = new ArrayList();
        list2.Add("A");
        list2.Add("B");
        list2.Add("C");
        list2.Add("D");
        list2.Add("E");
        list2.Add("F");
        list2.Add("G");
        list2.Add("H");
        list2.Add("I");

        Console.WriteLine("Elements in ArrayList2...");
        foreach (string res in list2) {
            Console.WriteLine(res);
        }

        ArrayList list3 = new ArrayList();
        Console.WriteLine("Current capacity of ArrayList3: " + list3.Capacity);
        list3 = list2;
        Console.WriteLine("Current capacity of ArrayList3 (Updated): " + list3.Capacity);
        Console.WriteLine("Is ArrayList3 equal to ArrayList2? = " + list3.Equals(list2));
        Console.WriteLine("Count of elements in ArrayList2 = " + list2.Count);
        list2.Clear();
        Console.WriteLine("Count of elements in ArrayList2 (Updated) = " + list2.Count);
    }
}

The output of the above code is −

Elements in ArrayList1...
A
B
C
D
E
F
G
H
I
Elements in ArrayList2...
A
B
C
D
E
F
G
H
I
Current capacity of ArrayList3: 0
Current capacity of ArrayList3 (Updated): 16
Is ArrayList3 equal to ArrayList2? = True
Count of elements in ArrayList2 = 9
Count of elements in ArrayList2 (Updated) = 0

Demonstrating Count and Capacity Relationship

Example

using System;
using System.Collections;

public class Demo {
    public static void Main(String[] args) {
        ArrayList list = new ArrayList();
        
        Console.WriteLine("Initial Count: " + list.Count);
        Console.WriteLine("Initial Capacity: " + list.Capacity);
        
        // Add elements one by one
        for (int i = 1; i <= 5; i++) {
            list.Add("Item" + i);
            Console.WriteLine("After adding Item{0} - Count: {1}, Capacity: {2}", i, list.Count, list.Capacity);
        }
        
        // Remove some elements
        list.RemoveAt(0);
        list.RemoveAt(0);
        Console.WriteLine("After removing 2 elements - Count: " + list.Count + ", Capacity: " + list.Capacity);
    }
}

The output of the above code is −

Initial Count: 0
Initial Capacity: 0
After adding Item1 - Count: 1, Capacity: 4
After adding Item2 - Count: 2, Capacity: 4
After adding Item3 - Count: 3, Capacity: 4
After adding Item4 - Count: 4, Capacity: 4
After adding Item5 - Count: 5, Capacity: 8
After removing 2 elements - Count: 3, Capacity: 8

Practical Use of Count Property

Example

using System;
using System.Collections;

public class Demo {
    public static void Main(String[] args) {
        ArrayList numbers = new ArrayList();
        numbers.Add(10);
        numbers.Add(20);
        numbers.Add(30);
        numbers.Add(40);
        numbers.Add(50);
        
        Console.WriteLine("Total elements: " + numbers.Count);
        
        // Check if ArrayList is empty
        if (numbers.Count == 0) {
            Console.WriteLine("ArrayList is empty");
        } else {
            Console.WriteLine("ArrayList contains " + numbers.Count + " elements");
        }
        
        // Access last element using Count
        if (numbers.Count > 0) {
            Console.WriteLine("Last element: " + numbers[numbers.Count - 1]);
        }
        
        // Loop using Count property
        Console.WriteLine("All elements:");
        for (int i = 0; i < numbers.Count; i++) {
            Console.WriteLine("Element at index " + i + ": " + numbers[i]);
        }
    }
}

The output of the above code is −

Total elements: 5
ArrayList contains 5 elements
Last element: 50
All elements:
Element at index 0: 10
Element at index 1: 20
Element at index 2: 30
Element at index 3: 40
Element at index 4: 50

Conclusion

The Count property is essential for determining the actual number of elements in an ArrayList. Unlike Capacity, it reflects the real data size and is commonly used for loops, bounds checking, and conditional operations when working with ArrayList collections.