Ttykuu

Thank you Henrik Hansen for the amazing code review. Here is the new LinkedList class and accompanying unit test after suggestions made by Henrik Hansen.

Here's the link to the previous code review:
Linked list implementation along with unit test

Implementation

/*************************************************************************************************************
 *
 * Special Thanks to Henrik Hansen for the awesome code review!
 * Url: https://codereview.stackexchange.com/questions/216453/linked-list-implementation-along-with-unit-test
 *
 *************************************************************************************************************/

using System;
using System.Collections;
using System.Collections.Generic;

namespace DataStructuresAndAlgorithms.DataStructures

 public class LinkedList<T> : IEnumerable<T>
 
 class Node
 
 public T Data get; 
 public Node Next get; set; 
 public Node Previous get; set; 

 public Node(T data)
 
 Data = data;
 
 

 private Node _head, _tail;
 public T Head => _head == null ? throw new ArgumentNullException("Head is null") : _head.Data;
 public T Tail => _tail == null ? throw new ArgumentNullException("Tail is null") : _tail.Data;

 public LinkedList() 

 public LinkedList(IEnumerable<T> items)
 
 foreach (var item in items)
 
 AddTail(item);
 
 

 public void AddHead(T item)
 
 if (item == null)
 throw new ArgumentNullException("AddHead: An item you are trying to add is not initialized!");

 if (_head == null && _tail == null)
 
 _head = new Node(item);
 _tail = _head;
 
 else
 
 _head.Previous = new Node(item);
 var temp = _head;
 _head = _head.Previous;
 _head.Next = temp;
 
 

 public void AddTail(T item)
 
 if (item == null)
 throw new ArgumentNullException("AddTail: An item you are trying to add is not initialized!");

 if (_tail == null && _head == null)
 
 _tail = new Node(item);
 _head = _tail;
 
 else
 
 _tail.Next = new Node(item);
 var temp = _tail;
 _tail = _tail.Next;
 _tail.Previous = temp;
 
 

 public void RemoveHead()
 
 if (_head == null) return;
 else
 
 _head = _head.Next;
 if (_head == null) return;
 _head.Previous = null;
 
 

 public void RemoveTail()
 
 if (_tail == null) return;
 else
 
 _tail = _tail.Previous;
 if (_tail == null) return;
 _tail.Next = null;
 
 

 public bool Remove(T item)
 
 var pointer = _head;
 while (pointer.Data.Equals(item) == false)
 
 if (pointer.Next == null)
 return false;
 pointer = pointer.Next;
 

 if (pointer.Previous == null)
 
 // It is the Head
 pointer.Next.Previous = null;
 return true;
 
 if (pointer.Next == null)
 
 // It is the Tail
 pointer.Previous.Next = null;
 return true;
 
 pointer.Previous.Next = null;
 pointer.Next.Previous = null;
 return true;
 

 public IEnumerator<T> GetEnumerator()
 
 var pointer = _head;
 while (pointer != null)
 
 yield return pointer.Data;
 pointer = pointer.Next;
 
 

 IEnumerator IEnumerable.GetEnumerator()
 
 return GetEnumerator();
 
 

Unit Test

using System;
using Xunit;

using DataStructuresAndAlgorithms.DataStructures;

namespace DataStructuresAndAlgorithms.DataStructures.Tests

 public class LinkedListTest
 
 [Fact]
 public void AddHead_Node_Should_Become_Head()
 
 // Arrange
 int[] myNums = 1, 2, 3, 4, 5 ;
 var myLinkedList = new LinkedList<int>(myNums);

 // Act
 myLinkedList.AddHead(45);

 // Assert
 Assert.Equal(45, myLinkedList.Head);
 

 [Fact]
 public void AddTail_Node_Should_Become_Tail()
 
 // Arrange
 int[] myNums = 1, 2, 3, 4, 5 ;
 var myLinkedList = new LinkedList<int>(myNums);

 // Act
 myLinkedList.AddTail(7777);

 // Assert
 Assert.Equal(7777, myLinkedList.Tail);
 

 [Fact]
 public void RemoveHead_Next_Node_Should_Be_Head()
 
 // Arrange
 int[] myNums = 1, 2, 3, 4, 5 ;
 var myLinkedList = new LinkedList<int>(myNums);

 // Act
 myLinkedList.RemoveHead();

 // Assert
 Assert.Equal(2, myLinkedList.Head);
 

 [Fact]
 public void RemoveTail_Next_Node_Should_Be_Tail()
 
 // Arrange
 int[] myNums = 1, 2, 3, 4, 5 ;
 var myLinkedList = new LinkedList<int>(myNums);

 // Act
 myLinkedList.RemoveTail();

 // Assert
 Assert.Equal(4, myLinkedList.Tail);
 
 

Presentation

using System;
using System.Collections;

using DataStructuresAndAlgorithms.DataStructures;

namespace DataStructuresAndAlgorithms.Presentation.Console

 class Program
 
 static void Main(string[] args)
 
 RunLinkedList();
 

 static void RunLinkedList()
 
 System.Console.WriteLine("Running the LinkedList class");
 System.Console.WriteLine("----------------------------");
 var myLinkedList = new LinkedList<int>();
 myLinkedList.AddHead(54);
 myLinkedList.AddHead(44);
 myLinkedList.AddHead(96);
 myLinkedList.AddTail(300);
 myLinkedList.AddTail(900);
 myLinkedList.AddTail(77);
 myLinkedList.Remove(900);

 System.Console.WriteLine("HEAD = " + myLinkedList.Head);
 System.Console.WriteLine("TAIL = " + myLinkedList.Tail);

 foreach (var item in myLinkedList)
 
 System.Console.WriteLine(item);
 
 
 

```