LinkedList in C#

The LinkedList<T> class in C# is a doubly-linked list implementation found in the System.Collections.Generic namespace. Unlike arrays or lists, a linked list allows for efficient insertion and removal of elements at any position without the need to shift other elements.

Each element in a LinkedList<T> is stored in a node that contains the data and references to both the next and previous nodes. This structure enables fast insertion and deletion operations at the cost of direct indexed access.

Syntax

Following is the syntax for creating a LinkedList −

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

Adding elements to the beginning or end −

linkedList.AddFirst(item);   // Add to beginning
linkedList.AddLast(item);    // Add to end

How LinkedList Works

Basic LinkedList Operations

Adding Elements

using System;
using System.Collections.Generic;

class Demo {
   static void Main() {
      LinkedList<string> linkedList = new LinkedList<string>();

      // Add elements
      linkedList.AddLast("First");
      linkedList.AddLast("Second");
      linkedList.AddFirst("Zero"); // Add at beginning
      linkedList.AddLast("Third");

      Console.WriteLine("LinkedList contents:");
      foreach(var element in linkedList) {
         Console.WriteLine(element);
      }

      Console.WriteLine("Count: " + linkedList.Count);
   }
}

The output of the above code is −

LinkedList contents:
Zero
First
Second
Third
Count: 4

Removing Elements

Example

using System;
using System.Collections.Generic;

class Demo {
   static void Main() {
      LinkedList<int> numbers = new LinkedList<int>();
      
      // Add some numbers
      numbers.AddLast(10);
      numbers.AddLast(20);
      numbers.AddLast(30);
      numbers.AddLast(40);

      Console.WriteLine("Original LinkedList:");
      foreach(var num in numbers) {
         Console.Write(num + " ");
      }

      // Remove operations
      numbers.RemoveFirst();     // Remove first element
      numbers.RemoveLast();      // Remove last element  
      numbers.Remove(20);        // Remove specific value

      Console.WriteLine("\nAfter removals:");
      foreach(var num in numbers) {
         Console.Write(num + " ");
      }
   }
}

The output of the above code is −

Original LinkedList:
10 20 30 40 
After removals:
30 

Working with LinkedListNode

Example

using System;
using System.Collections.Generic;

class Demo {
   static void Main() {
      LinkedList<string> cities = new LinkedList<string>();
      
      cities.AddLast("New York");
      cities.AddLast("London");
      cities.AddLast("Tokyo");

      // Find a specific node
      LinkedListNode<string> londonNode = cities.Find("London");
      
      if(londonNode != null) {
         // Insert before and after London
         cities.AddBefore(londonNode, "Paris");
         cities.AddAfter(londonNode, "Berlin");
      }

      Console.WriteLine("Cities in LinkedList:");
      foreach(var city in cities) {
         Console.WriteLine(city);
      }
   }
}

The output of the above code is −

Cities in LinkedList:
New York
Paris
London
Berlin
Tokyo

LinkedList vs List Comparison

Conclusion

LinkedList<T> in C# provides efficient insertion and deletion operations at any position through its doubly-linked structure. Use LinkedList when you need frequent modifications to the collection, but consider List<T> when you require indexed access to elements.