Multiform version 1

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication143
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Form2 RefTilNytVindue = new Form2();
            if (RefTilNytVindue.ShowDialog() == DialogResult.OK) MessageBox.Show("OK");

        }
    }
}