CODE:

//greet.h
#ifndef DEF_GREET
#define DEF_GREET

const wchar_t* greet(const wchar_t* name);

#endif

//greet.cpp
#include "greet.h"
#include 

const wchar_t* greet(const wchar_t* name)
{
	static wchar_t result[256];
	wcscpy_s(result, 256, name);
	wcscat_s(result, 256, L"さん、こんにちは");
	return result;
}

CODE:

//GreetLib.h
#pragma once

using namespace System;

public ref class GreetLib
{
public:
	static String^ Greet(String^ name);

};

//GreetLib.cpp
#include "GreetLib.h"
#include "greet.h"
#include "ConvString.h"

String^ GreetLib::Greet(String^ name){
	std::wstring input = ConvertCLIString::ToWideString(name); //CLI文字列をstd::wstringに変換
	std::wstring result = greet(input.c_str() ); //greet関数を呼び出す
	return ConvertCLIString::WideStringToCLI(result);  //std::wstringをCLI文字列に変換
}

CODE:

Public Class Form1

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        ResultText.Text = GreetLib.Greet(NameText.Text)
    End Sub
End Class