How to Go From Form1 to Form2 in Windows Application

I have two forms, form1 and form2 and I have a button1 on form 1. Now, when I click on the button1, the page shall redirect to form2.
 
After clicking on the button.
 
private void btn_Click(object sender, EventArgs e)
{
     this.Hide();
     form2  a1 = new form2();
     a1.ShowDialog();
}