Difference of two Linked Lists using Merge sort

using System;
class Node {
    public int data;
    public Node next;

    public Node(int data)
    {
        this.data = data;
        this.next = null;
    }
}

class LinkedList {
    public Node head;

    public LinkedList() { head = null; }

    // Function to insert a node at the end of Linked List
    public void Append(int data)
    {
        Node newNode = new Node(data);
        if (head == null) {
            head = newNode;
        }
        else {
            Node current = head;
            while (current.next != null) {
                current = current.next;
            }
            current.next = newNode;
        }
    }

    // Function to find the middle node of the Linked List
    public Node GetMid(Node head)
    {
        if (head == null) {
            return head;
        }
        Node slow = head;
        Node fast = head;
        while (fast.next != null
               && fast.next.next != null) {
            slow = slow.next;
            fast = fast.next.next;
        }
        return slow;
    }

    // Recursive method to merge two halves after sorting
    public Node Merge(Node left, Node right)
    {
        if (left == null) {
            return right;
        }
        if (right == null) {
            return left;
        }

        Node result;
        if (left.data <= right.data) {
            result = left;
            result.next = Merge(left.next, right);
        }
        else {
            result = right;
            result.next = Merge(left, right.next);
        }
        return result;
    }

    // Recursive method to divide the list into two halves
    // until 1 node left
    public Node MergeSort(Node head)
    {
        if (head == null || head.next == null) {
            return head;
        }

        Node mid = GetMid(head);
        Node nextToMid = mid.next;
        mid.next = null;
        Node left = MergeSort(head);
        Node right = MergeSort(nextToMid);
        return Merge(left, right);
    }

    // Function to print the list elements
    public void Display()
    {
        Node current = head;
        while (current != null) {
            Console.Write(current.data + " ");
            current = current.next;
        }
        Console.WriteLine();
    }

    // Function to get the difference list
    public static LinkedList GetDifference(Node p1, Node p2)
    {
        LinkedList differenceList = new LinkedList();

        // Scan the lists
        while (p1 != null && p2 != null) {
            // Condition to check if the data of both
            // pointers are the same, then move ahead
            if (p2.data == p1.data) {
                p1 = p1.next;
                p2 = p2.next;
            }
            else if (p2.data
                     < p1.data) // Condition to check if the
                                // data of the second
                                // pointer is smaller than
                                // the first, then move the
                                // second pointer ahead
            {
                p2 = p2.next;
            }
            else { // Condition when the data of the first
                   // pointer is greater than the second,
                   // then append into the difference list
                   // and move
                differenceList.Append(p1.data);
                p1 = p1.next;
            }
        }

        // If the end of list2 is reached, there may be some
        // nodes in List 1 left to be scanned, they all will
        // be inserted in the difference list
        while (p1 != null) {
            differenceList.Append(p1.data);
            p1 = p1.next;
        }

        return differenceList;
    }
}

class Program {
    public static void Main(string[] args)
    {
        // Linked List 1
        LinkedList list1 = new LinkedList();
        list1.Append(2);
        list1.Append(6);
        list1.Append(8);
        list1.Append(1);

        // Linked List 2
        LinkedList list2 = new LinkedList();
        list2.Append(4);
        list2.Append(1);
        list2.Append(9);

        // Sort both the linked lists
        list1.head = list1.MergeSort(list1.head);
        list2.head = list2.MergeSort(list2.head);

        // Get the difference list
        LinkedList result = LinkedList.GetDifference(
            list1.head, list2.head);

        if (result.head != null) {
            result.Display();
        }
        else {
            Console.WriteLine("Lists are equal");
        }
    }
}