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