Merge Two Sorted List

MergeTwoList.cs

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     public int val;
 *     public ListNode next;
 *     public ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode MergeTwoLists(ListNode l1, ListNode l2) {
        
        if(l1 == null && l2 == null) return null;
        
        if(l1 != null && l2 == null) return l1;
        
        if(l2 != null && l1 == null) return l2;
        
        ListNode newHead = null;
        
        if(l1.val < l2.val){
            newHead = l1;
            newHead.next = MergeTwoLists(l1.next, l2);
        }
        
        else
        {
            newHead = l2;
            newHead.next = MergeTwoLists(l1, l2.next);
        }
        
        return newHead;
    }
}