How to show a form again after hiding it?

问题

I have two forms. I need to open a second form with a button. When I open form2 I hide form1. However when I try to show form1 again from form2 with a button it doesn't work. My form1 code is:

Form2 form2 = new Form2();        
form2.ShowDialog();

Inside form2 code:

Form1.ActiveForm.ShowDialog();

or

Form1.ActiveForm.Show();

or

form1.show(); (form1 doesn't exist in the current context)

doesn't work. I do not want to open a new form

Form1 form1 = new Form1();   
form1.ShowDialog();

I want show the form which I hided before. Alternatively I can minimize it to taskbar

this.WindowState = FormWindowState.Minimized;

and maximize it from form2 again.

Form2.ActiveForm.WindowState = FormWindowState.Maximized;

however the way I am trying is again doesn't work. What is wrong with these ways?

回答1:

You could try (on Form1 button click)

Hide();
Form2 form2 = new Form2();        
form2.ShowDialog();
form2 = null;
Show();

or (it should work)

Hide();
using (Form2 form2 = new Form2())       
    form2.ShowDialog();
Show();

回答2:

Preserve the instance of Form1 and use it to Show or Hide.

回答3:

You can access Form1 from Form2 throught the Owner property if you show form2 like this:

form2.ShowDialog( form1 )

or like this:

 form2.Show( form1 )

Notice this way you are not forced to use ShowDialog cause hide and show logic can be moved inside Form2

回答4:

This method is the one that I find works the best for me

Primary Form

Form2 form2 = new Form2(this);

Secondary Form

private Form Form1
public Form2(Form Form1)
{
    InitializeComponent();
    this.Form1 = Form1;
    Form1.Hide();
}

Later on when closing

private void btnClose_Click(object sender, EventArgs e)
{
    Form1.Show();
    this.Close();
}

来源：https://stackoverflow.com/questions/13233451/how-to-show-a-form-again-after-hiding-it