Largest smaller key value in binary search tree - code review - July 22, 2017

LargestSmallerKeyValueInBST.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace LargestSmallerBinarySearchTreeValue
{
    /// <summary>
    /// code review July 22, 2017
    /// </summary>
    public class Node{
        public int Key {get; set;}
        public Node Left {get; set;}
        public Node Right {get; set;}
    }

    class Program
    {
        static void Main(string[] args)
        {
        }

        /// <summary>
        /// get largest smaller key in binary search tree
        /// assuming that all numbers in the tree are nonnegative integer. 
        /// </summary>
        /// <returns></returns>
        public static int GetLargestSmallerBSTKey(Node root, int number)
        {
            if(root == null)
            {
                return -1; 
            }

            var visit = root.Key;
            bool searchIsSmaller = number <= visit; 

            if(searchIsSmaller)
            {
                return GetLargestSmallerBSTKey(root.Left, number); 
            }

            // assuming that visit < number
            var candiate = visit;
            return Math.Max(candiate, GetLargestSmallerBSTKey(root.Right, number)); 
        }
    }
}