Binary Tree in C++/CLI with value is System::String - visual-c++

Question

I have a problem when i try to insert node to binary tree. I don't understand why the argument is always null. Here is my program.
file "BinaryTree.h"
#pragma once
#ifndef BINARYTREE_H
#define BINARYTREE_H
using namespace System;
ref class BinaryTree
{
public:
BinaryTree()
{
root = nullptr;
};
~BinaryTree()
{
destroySubtree(root);
};
void insertNode(String^);
bool searchNode(String^);
void remove(String^);
String^ disPlay()
{
return disPlay(root);
};
private:
ref struct TreeNode
{
String^ values;
TreeNode ^left;
TreeNode ^right;
};
TreeNode ^root;
void insert(TreeNode ^, TreeNode ^);
void deleteNode(String^, TreeNode ^);
void destroySubtree(TreeNode ^);
void makeDeletion(TreeNode ^);
String^ disPlay(TreeNode ^);
};
#endif
And here is file "BinaryTree.cpp"
#include "BinaryTree.h"
using namespace System;
void BinaryTree::insert(TreeNode ^node, TreeNode ^newNode)
{
if (node == nullptr)
node = newNode;
else if (newNode->values->CompareTo(node->values)<0)
insert(node->left, newNode);
else
insert(node->right, newNode);
}
void BinaryTree::insertNode(String^ s)
{
TreeNode ^newNode = gcnew TreeNode;
newNode->values->Copy(s);
newNode->left = newNode->right = nullptr;
insert(root, newNode);
}
bool BinaryTree::searchNode(String^ s)
{
TreeNode ^node = root;
while (node)
{
if (node->values->CompareTo(s)==0)
return true;
else if (node->values->CompareTo(s) > 0)
node = node->left;
else
node = node->right;
}
return false;
}
void BinaryTree::remove(String^ s)
{
deleteNode(s, root);
}
void BinaryTree::deleteNode(String^ s,TreeNode ^node)
{
if (node->values->CompareTo(s) > 0)
deleteNode(s, node->left);
else if (node->values->CompareTo(s) < 0)
deleteNode(s, node->right);
else
makeDeletion(node);
}
void BinaryTree::makeDeletion(TreeNode ^node)
{
TreeNode ^tempNode;
if (node == nullptr){}
else if (node->right == nullptr)
{
tempNode = node;
node = node->left;
delete tempNode;
}
else if (node->left == nullptr)
{
tempNode = node;
node = node->right;
delete tempNode;
}
else
{
tempNode = node->right;
while (node->left)
{
tempNode = tempNode->left;
}
tempNode->left = node->left;
tempNode = node;
node = node->right;
delete tempNode;
}
}
void BinaryTree::destroySubtree(TreeNode ^node)
{
if (node)
{
if (node->left)
{
destroySubtree(node->left);
}
if (node->right)
{
destroySubtree(node->right);
}
delete node;
}
}
String^ BinaryTree::disPlay(TreeNode ^node)
{
String^ s;
if (node)
{
s = node->values;
return s+=disPlay(node->left);
return s+=disPlay(node->right);
}
return s;
}
When I use like this:
BinaryTree^ Tree = gcnew BinaryTree();
string key="abc0123456";
String^ sss = gcnew String(key.c_str());
Tree->insertNode(sss);
MessageBox::Show(Tree->disPlay());
but the result always null,when i check at step "Tree->insertNode(sss);" then the argument "sss" in function "insertNode(String^ s)", it mean variable "s" is null.
What should i do now to fix this problem?
Anyone can help me pls

Answer 1

Because String.Copy is static method, I believe. It returns back string which is not assigned to value field anywhere in you code
Something like
newNode->values = String::Copy(s);
might work

Answer 2

Your disPlay method will not recurse to right branches ever, Because it returns values + left recursion only.
I believe your intentios was something more like this:
String BinaryTree::disPlay(TreeNode ^node)
{
String s;
if (node)
{
s = node->values;
s+=disPlay(node->left);
s+=disPlay(node->right);
}
return s;
}