Solution Review: Finding the Height of a Binary Tree

using System;
namespace chapter_6
{
    class Solution
    {
        static int findHeight(Node rootNode)
        {
            if (rootNode == null)
                return -1;
            else
            {
                // Find Height of left subtree and then right subtree
                // Return greater height value of left or right subtree (plus 1)
                int leftHeight = findHeight(rootNode.leftChild);
                int rightHeight = findHeight(rootNode.rightChild);
                if (leftHeight > rightHeight)
                    return leftHeight + 1;
                else
                    return rightHeight + 1;
            }
        }
        static void Main(string[] args)
        {
            BinarySearchTree BST = new BinarySearchTree(6);
            BST.insertBST(4);
            BST.insertBST(9);
            BST.insertBST(5);
            BST.insertBST(2);
            BST.insertBST(8);
            BST.insertBST(12);
            Console.WriteLine(findHeight(BST.getRoot()));
        }
    }
}