C# List

List<T> is a class that contains multiple objects of the same data type that can be accessed using an index. For example,

// list containing integer values 
List<int> number = new List<int>() { 1, 2, 3 };

Here, number is a List containing integer values (1, 2 and 3).

Create a List

To create List<T> in C#, we need to use the System.Collections.Generic namespace. Here is how we can create List<T>.For example,

using System;
using System.Collections.Generic;
class Program
{
    public static void Main()
    {
        // create a list named subjects that contain 2 elements 
        List<string> subjects = new List<string>() { "English", "Math" };
    }
}

Access the List Elements

We can access List using index notation []. For example,

using System;
using System.Collections.Generic;

class Program
{
    public static void Main()
    {
        // create a list
        List<string> languages = new List<string>() { "Python", "Java" };

        // access the first and second elements of languages list
        Console.WriteLine("The first element of the list is " + languages[0]);
        Console.WriteLine("The second element of the list is " + languages[1]);
    }
}

Output

The first element of the list is Python
The second element of the list is Java

Since the index of the list starts from 0:

• language[0] - accesses the first element
• language[5] - accesses the fourth element

Iterate the List

In C#, we can also loop through each element of List<T> using a for loop. For example,

using System;
using System.Collections.Generic;

class Program
{
    public static void Main()
    {
        // create a list
        List<string> albums = new List<string>() { "Red", "Midnight", "Reputation" };

        // iterate through the albums list  
        for (int i = 0; i < albums.Count; i++)
            Console.WriteLine(albums[i]);
    }
}

Output

Red
Midnight
Reputation

In the above example, we have looped through the albums list using a for loop.

Note: The Count property returns the total number of elements inside the list.

Basic Operations on List

The List<T> class provides various methods to perform different operations on List. We will look at some commonly used List operations in this tutorial:

• Add Elements
• Insert Elements
• Remove Elements

Let's discuss each operation in detail.

Add Elements to List

To add a single element to the List, we use the Add() method of the List<T> class. For example,

using System;
using System.Collections.Generic;

class Program
{
    public static void Main()
    {
        // create a list
        List<string> country = new List<string>() { "Russia" };

        //add "USA" to the country list
        country.Add("USA");

        // add "Japan" to the country list 
        country.Add("Japan");

        // iterate through the country list  
        for (int i = 0; i < country.Count; i++)
            Console.WriteLine(country[i]);
    }
}

Output

Russia
USA
Japan

In the above example, at first, we have created a country list that contains "Russia".

Then we added "USA" and "Japan" to the list using the Add() method.

Insert Element in a List

To insert an element to a specified index in List, we use the Insert() method of the List<T> class. For example,

using System;
using System.Collections.Generic;

class Program
{
    public static void Main()
    {
        // create a list
        List<string> languages = new List<string>() { "Python", "Java", "C" };

        // insert "JavaScript" at index 2
        languages.Insert(2, "JavaScript");
        
        // display element at index 2
        Console.WriteLine(languages[2]);
    }
}

Output

JavaScript

In the above example,

• languages.Insert(2, "JavaScript") inserts "JavaScript" at the 2nd index position

Remove Elements from the List

We can delete one or more items from List<T> using 2 methods:

• Remove() - removes the first occurrence of an element from the given list
• RemoveAt() - removes the elements at the specified position in the list

Let's see examples using both methods.

Example: Remove() Method

using System;
using System.Collections.Generic;

class Program
{
    public static void Main()
    {
        var car = new List<string>() { "BMW", "Tesla", "Suzuki", "Tesla" };

        // remove the first occurence of "Tesla" from the list
        car.Remove("Tesla");

        // remove the first occurrence of "Suzuki" 
        car.Remove("Suzuki");

        // print the updated list after removing   
        for (int i = 0; i < car.Count; i++)
        {
            Console.WriteLine(car[i]);

        }
    }
}

Output

BMW
Tesla

Here,

• car.Remove("Tesla") - removes the first occurrence of "Tesla"
• car.Remove("Suzuki) - removes the first occurrence of "Suzuki"

We can see that,

• The original list: { "BMW", "Tesla", "Suzuki", "Tesla" }
• The modified list: {"BMW", "Tesla"}

Example: RemoveAt() Method

using System;
using System.Collections.Generic;

class Program
{
    public static void Main()
    {
        var car = new List<string>() { "BMW", "Tesla", "Suzuki", "Tesla" };

        // remove the element present at the 2nd index position
        car.RemoveAt(2);

        // print the updated list after removing the element  
        for (int i = 0; i < car.Count; i++)
        {
            Console.WriteLine(car[i]);

        }
    }
}

Output

BMW
Tesla
Tesla

In the above example, we have removed the element of List<T> using the RemoveAt() method.

Here, car.RemoveAt(2) removes "Suzuki" from the list.

using System;
using System.Collections.Generic;

class Program
{
    public static void Main()
    {
        // create a list named color 
        var color = new List<string>() {
            "Red",
            "Blue",
            "Pink"
        };

        Console.WriteLine(color[2]);
    }
}

Pink