public void Add(string firstName, string lastName, string email)
        {
            if (Head == null)
            {
                // Create node as head if no node exists and add data to it
                Head = new CustomLinkedListNode()
                {
                    Data = new Person()
                    {
                        FirstName = firstName, LastName = lastName, Email = email
                    }
                };
                return;
            }
            // Assign Head as the current node
            CustomLinkedListNode current = Head;

            // Loop to find the last node without the Next pointer
            while (current.Next != null)
            {
                current = current.Next;
            }
            // Create new node at the end of the last node
            current.Next = new CustomLinkedListNode()
            {
                Data = new Person()
                {
                    FirstName = firstName, LastName = lastName, Email = email
                }
            };
            current.Next.Previous = current;
        }
        public bool InsertAfter(string firstName, string lastName, string email, CustomLinkedListNode n)
        {
            // Create node
            CustomLinkedListNode newNode = new CustomLinkedListNode()
            {
                Data = new Person()
            };

            // Searching for the selected value in the head and inserting new node after the head
            if (Head.Data.Email == n.Data.Email)
            {
                newNode.Data.FirstName = firstName;
                newNode.Data.LastName  = lastName;
                newNode.Data.Email     = email;
                newNode.Next           = Head.Next;
                Head.Next     = newNode;
                Head.Previous = null;
                return(true);
            }
            else
            {
                // Assign Head as the current node
                CustomLinkedListNode current = Head;
                // Searching for the selected value in other nodes and inserting new node after the node with the match
                while (current.Next != null)
                {
                    if (current.Data.Email == n.Data.Email)
                    {
                        newNode.Data.FirstName = firstName;
                        newNode.Data.LastName  = lastName;
                        newNode.Data.Email     = email;
                        newNode.Next           = current.Next;
                        current.Next           = newNode;
                        current.Next.Previous  = current.Previous.Previous;
                        return(true);
                    }
                    current = current.Next;
                }
                if (current.Data.Email == n.Data.Email && current.Next == null)
                {
                    newNode.Data.FirstName = firstName;
                    newNode.Data.LastName  = lastName;
                    newNode.Data.Email     = email;
                    newNode.Next           = null;
                    current.Next           = newNode;
                    current.Next.Previous  = current.Previous.Previous;
                    return(true);
                }
                return(false);
            }
        }
 public CustomLinkedListNode Find(string email)
 {
     // Checking if Head match the data
     if (Head.Data.Email == email)
     {
         return(Head);
     }
     else
     {
         // Assign Head as the current node
         CustomLinkedListNode current = Head;
         //If value not found in the head, looping through all other nodes for the value
         while (current.Next != null)
         {
             if (current.Next.Data.Email == email)
             {
                 return(current.Next);
             }
             current = current.Next;
         }
         return(null);
     }
 }
        public void Remove(string email)
        {
            // If head node dont exists throw back exception
            if (Head == null)
            {
                throw new NullReferenceException($"Brugeren med email: {email} findes ikke");
            }
            // If head match the data, point the head to the next node
            if (Head.Data.Email == email && Head.Next != null)
            {
                Head          = Head.Next;
                Head.Previous = null;
                return;
            }
            else if (Head.Data.Email == email && Head.Next == null)
            {
                Head = null;
                return;
            }
            // Assign Head as the current node
            CustomLinkedListNode current = Head;

            // Looping through other nodes, if there is a match point the node to the next node
            while (current.Next != null)
            {
                if (current.Next.Data.Email == email)
                {
                    current.Next     = current.Next.Next;
                    current.Previous = current;
                    return;
                }
                current = current.Next;
            }
            // If no match throw back exception
            throw new NullReferenceException($"Brugeren med email: {email} findes ikke");
        }