C# LinkedList<T>

The LinkedList<T> class is used to store a collection of elements as a linked list. It allows fast insertion and deletion of elements and can store duplicate values.

In this chapter, you will learn what the LinkedList<T> class is, how to create and use it, its commonly used methods, and practical examples.

What is LinkedList<T> in C#?

The LinkedList<T> class is available in the System.Collections.Generic namespace and is used to store elements in the form of linked nodes. Each element is stored in a separate node that is connected to the next and previous nodes. It allows efficient insertion and deletion of elements at the beginning, end, or around a specific node. Unlike List<T>, it does not support direct indexing.

Creating a Generic LinkedList<T> in C#

A generic LinkedList<T> is created by using the LinkedList<T> class. Elements can be added by using methods such as AddFirst(), AddLast(), AddBefore(), and AddAfter().

Syntax

The following syntax is used to create a generic LinkedList<T> in C#:

LinkedList<T> listName = new LinkedList<T>();

In this syntax:

• LinkedList<T>: It specifies the generic linked list class.
• T: It specifies the data type of the elements, such as int, string, or char.
• listName: It specifies the name of the linked list object.
• new LinkedList<T>(): It creates an empty linked list.

Common Methods of the LinkedList<T> Class

The following table demonstrate several methods of the LinkedList<T> Class.

Note: Unlike List<T>, a LinkedList<T> cannot be initialized by using a collection initializer.

Examples of the LinkedList<T> Class

The following examples demonstrate how to use the LinkedList<T> class to store and manage data.

Example 1: Adding Elements to a LinkedList<T>

This example shows how to add elements to the beginning and end of a linked list by using the AddFirst() and AddLast() methods.

using System;
using System.Collections.Generic;

public class LinkedListExample
{
    public static void Main(string[] args)
    {
        // Create a list of strings
        var names = new LinkedList<string>();
        names.AddLast("Sonoo Jaiswal");
        names.AddLast("Ankit");
        names.AddLast("Peter");
        names.AddLast("Irfan");
        names.AddFirst("John");//added to first index

        // Iterate list element using foreach loop
        foreach (var name in names)
        {
            Console.WriteLine(name);
        }
    }
}

Output:

John
Sonoo Jaiswal
Ankit
Peter
Irfan

Explanation

In this example, we create a LinkedList<string> and add elements by using the AddLast() method. After that, we use the AddFirst() method to insert "John" at the beginning of the linked list. Finally, we use a foreach loop to display all the elements.

Example 2: Inserting Elements Before and After a Node

This example demonstrates how to locate a node by using the Find() method and insert new elements before and after it by using the AddBefore() and AddAfter() methods.

using System;
using System.Collections.Generic;

public class LinkedListExample
{
    public static void Main(string[] args)
    {
        // Create a list of strings
        var names = new LinkedList<string>();
        names.AddLast("Sonoo");
        names.AddLast("Ankit");
        names.AddLast("Peter");
        names.AddLast("Irfan");
        
        //insert new element before "Peter"
        LinkedListNode<String> node=names.Find("Peter");
        names.AddBefore(node, "John");
        names.AddAfter(node, "Lucy");

        // Iterate list element using foreach loop
        foreach (var name in names)
        {
            Console.WriteLine(name);
        }
    }
}

Output:

Sonoo
Ankit
John
Peter
Lucy
Irfan

Explanation

In this example, we first create a LinkedList<string> and add several names by using the AddLast() method. Next, we locate the node containing "Peter" by using the Find() method. After that, we insert "John" before "Peter" by using AddBefore() and "Lucy" after "Peter" by using AddAfter(). Finally, we use a foreach loop to display the updated linked list.