error LNK2020: unresolved token (06000001) write_functions::WritePaths
error LNK1120: 1 unresolved externals

#pragma once

#include <string>
#include <utility>
#include <fstream>
#include <sstream>

using namespace System;
using namespace System::ComponentModel;
using namespace System::Collections;
using namespace System::Windows::Forms;
using namespace System::Data;
using namespace System::Drawing;

ref class write_functions
{
public:

private:

   std::pair<bool,std::string> WritePaths(System::Windows::Forms::RichTextBox^ Box);
};