call metode from class

FORM1

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
HappyBirthday birthdayMessage;
birthdayMessage = new HappyBirthday();
MessageBox.Show(birthdayMessage.getMessage());
}
}
}

CLASS

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace WindowsFormsApplication1
{
class HappyBirthday
{
public string getMessage()
{
return "happy Birthday";
}
}
}