Sum of all right leaf nodes of binary tree in c#

Csharp program for Sum of all right leaf nodes of binary tree. Here mentioned other language solution.

// Include namespace system
using System;
/*
    Csharp program for
    Sum of all right leaves nodes in a binary 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;
	}
	// Display pre order elements
	public void preorder(TreeNode node)
	{
		if (node != null)
		{
			// Print node value
			Console.Write("  " + node.data);
			this.preorder(node.left);
			this.preorder(node.right);
		}
	}
	// Returns the Sum of all the right leaves in binary tree
	public int rightLeavesSum(TreeNode node)
	{
		var sum = 0;
		if (node != null)
		{
			if (node.right != null && 
                node.right.left == null && 
                node.right.right == null)
			{
				// When get right leaf node
				sum = node.right.data;
			}
			// Recursively visit left and right subtree.
			// And find sum of right leaf nodes
			sum = sum + this.rightLeavesSum(node.left) +
              this.rightLeavesSum(node.right);
		}
		return sum;
	}
	public static void Main(String[] args)
	{
		// New binary tree
		var tree = new BinaryTree();
		/*
		    Constructor binary tree
		    -----------------------
		          6
		         / \ 
		        /   \                             
		       /     \    
		      2       3     
		     / \       \               
		    8   10      1
		       /  \    / \
		      6   -2  4   5
		*/
		// Add tree node
		tree.root = new TreeNode(6);
		tree.root.left = new TreeNode(2);
		tree.root.left.left = new TreeNode(8);
		tree.root.left.right = new TreeNode(10);
		tree.root.left.right.right = new TreeNode(-2);
		tree.root.left.right.left = new TreeNode(6);
		tree.root.right = new TreeNode(3);
		tree.root.right.right = new TreeNode(1);
		tree.root.right.right.left = new TreeNode(4);
		tree.root.right.right.right = new TreeNode(5);
		Console.Write("\n Tree Nodes : ");
		tree.preorder(tree.root);
		// Find right leaf sum
		var sum = tree.rightLeavesSum(tree.root);
		// Display result
		Console.Write("\n Right leaves nodes sum : " + sum);
	}
}

Output

 Tree Nodes :   6  2  8  10  6  -2  3  1  4  5
 Right leaves nodes sum : 3