C# | Adding an element to the List

Last Updated : 11 Jul, 2025

List.Add(T) Method is used to add an object to the end of the List. Properties of List:

It is different from the arrays. A list can be resized dynamically but arrays cannot.
List class can accept null as a valid value for reference types and it also allows duplicate elements.
If the Count becomes equals to Capacity then the capacity of the List increases automatically by reallocating the internal array. The existing elements will be copied to the new array before the addition of the new element.
If the Count is less than Capacity then this method is an O(1) operation. If the capacity needs to be increased to accommodate the new element then this method becomes an O(n) operation.

Syntax:

public void Add (T item);

Parameter:

item: Specified object which is to be added to the end of the List of type System.Object.

Below programs illustrate how to add an element in List: Example 1:

CSharp

// C# program to add element in List<T>
using System;
using System.Collections.Generic;

class Geeks {

    // Main Method
    public static void Main(String[] args)
    {

        // Creating a List of integers
        List<int> firstlist = new List<int>();

        // adding elements in firstlist
        for (int i = 4; i < 10; i++) {
            firstlist.Add(i * 2);
        }

        // Displaying elements of firstlist
        // by using foreach loop
        foreach(int element in firstlist)
        {
            Console.WriteLine(element);
        }
    }
}

Output:

Example 2:

CSharp

// C# program to add element in List<T>
using System;
using System.Collections.Generic;

class Geeks {

    // Main Method
    public static void Main(String[] args)
    {

        // Creating a List of integers
        List<int> firstlist = new List<int>();

        // adding elements in firstlist
        firstlist.Add(1);
        firstlist.Add(2);
        firstlist.Add(3);
        firstlist.Add(4);

        // Adding some duplicate
        // elements in firstlist
        firstlist.Add(3);
        firstlist.Add(4);

        // Displaying elements of firstlist
        // by using foreach loop
        foreach(int element in firstlist)
        {
            Console.WriteLine(element);
        }
    }
}