単純にこれで良いのではないでしょうか。
C#
1namespace WindowsFormsApplication1
2{
3 public partial class Form1 : Form
4 {
5 public Form1()
6 {
7 InitializeComponent();
8 }
9
10 private void button1_Click(object sender, EventArgs e)
11 {
12 this.Visible = false;
13
14 Form2 f2 = new Form2();
15 f2.Show();
16 }
17
18 private void Form1_FormClosing(object sender, FormClosingEventArgs e)
19 {
20 Application.Exit();
21 }
22 }
23}
24
C#
1namespace WindowsFormsApplication1
2{
3 public partial class Form2 : Form
4 {
5 public Form2()
6 {
7 InitializeComponent();
8 }
9
10 private void Form2_FormClosing(object sender, FormClosingEventArgs e)
11 {
12 Form1 f1 = new Form1();
13
14 f1.Visible = true;
15 }
16 }
17}