Form1:
private void button1_Click(object sender, System.EventArgs e)
{
Form2.InstanceForm = new Form2();
Form2.InstanceForm.Show();
}
private void button2_Click(object sender, System.EventArgs e)
{
Form2.InstanceForm.Close();
}
Form2:
public class Form2 : System.Windows.Forms.Form
{
public static Form2 InstanceForm = null;