C# Form1隐藏，在Form2关闭时显示Form1

//Form1private void button1_Click(object sender ,EventArgs e){    this.Hide();    Form2 f = new Form2(this);    f.Show();}//Form2Form1 fr =null;public 管理员界面(Form1 f)//Login f{    fr = f;    InitializeComponent();}private void btnClose_Click(object sender ,EventArgs e){    this.Close();}private void Form2_FormClosing(object sender, FormClosingEventArgs e){    fr.Show();}