Check for continuous binary tree in c#

Csharp program for Check for continuous binary tree. Here problem description and other solutions.

// Include namespace system
using System;
/* 
  Csharp program for
  Check if binary tree is continuous tree
  Using recursion
*/
// Binary Tree Node
public class TreeNode
{
	public int data;
	public TreeNode left;
	public TreeNode right;
	public TreeNode(int data)
	{
		// Set node value
		this.data = data;
		this.left = null;
		this.right = null;
	}
}
public class BinaryTree
{
	public TreeNode root;
	public BinaryTree()
	{
		// Set initial tree root
		this.root = null;
	}
	public int absValue(int num)
	{
		if (num < 0)
		{
			return -num;
		}
		return num;
	}
	// Check tree is continuous or not
	public bool isContinuous(TreeNode node)
	{
		if (node != null)
		{
			if ((node.left != null && 
                 this.absValue(node.data - node.left.data) != 1) || 
                (node.right != null && 
                 this.absValue(node.data - node.right.data) != 1))
			{
				// Case
				// When fail continuous tree rule
				return false;
			}
			if (this.isContinuous(node.left) && 
                this.isContinuous(node.right))
			{
				return true;
			}
			// When node value is not satisfied
			//  continuous tree properties
			return false;
		}
		return true;
	}
	public static void Main(String[] args)
	{
		// Create new tree
		var tree = new BinaryTree();
		/*  
		   Binary Tree
		   ------------
		       5
		     /   \
		    4     4
		   /     /  \
		  3     5    3
		   \
		    2
		        
		*/
		// Add tree node
		tree.root = new TreeNode(5);
		tree.root.left = new TreeNode(4);
		tree.root.right = new TreeNode(4);
		tree.root.left.left = new TreeNode(3);
		tree.root.right.right = new TreeNode(3);
		tree.root.right.left = new TreeNode(5);
		tree.root.left.left.right = new TreeNode(2);
		if (tree.isContinuous(tree.root) == true)
		{
			Console.WriteLine("Continuous Tree ");
		}
		else
		{
			Console.WriteLine("Not Continuous Tree ");
		}
		// Case 2
		/* 
		       5
		     /   \
		    4     4
		   /     /  \
		  3     5    3
		   \
		    1  <--- change value
		        
		*/
		tree.root.left.left.right.data = 1;
		if (tree.isContinuous(tree.root) == true)
		{
			Console.WriteLine("Continuous Tree ");
		}
		else
		{
			Console.WriteLine("Not Continuous Tree ");
		}
	}
}

Output

Continuous Tree
Not Continuous Tree