您可以覆盖

   保护覆盖无效OnFormClosing（FormClosingEventArgs e）
 {
 if（e.CloseReason == CloseReason.WindowsShutDown）return; 

 //在此处进行
} 
 

I would like to make X control closing window to hide current display previous form.

In form1 I got:

private void button1_Click(object sender, EventArgs e)
{
    Form2 form2 = new Form2();
    form2.Tag = this;
    form2.Show(this);
    Hide();
}

and then when I click X I would like to show previous and hide the current.

You can override OnFormClosing to do this.

 protected override void OnFormClosing(FormClosingEventArgs e)
{
    if (e.CloseReason == CloseReason.WindowsShutDown) return;

    // DO WHATEVER HERE
}