Windows Forms C#

I am learning windows forms and can create a one form with textboxes and stuff, but I was wondering how can I change the form upon let's say clickin开发者_如何学编程g a button?, so for instance my initial form has a textbox and a button, if the button is clicked I want to show a form with a dropdown and a button. SO the question should be:

1) How do I change the form upon clicking a button but without creating a new instance of the form.

2) If I wanted, how can I add a form when the button is clicked showing the same drop down and button as a pop up form?

In reality I would like to know both cases, changing the form via using the same form and via popping a new form on top.

Should the questions not be clear, I am willing to further explain

Thank you

I'm assuming you already know how to add controls in the form designer and how to implement event handlers.

Question 1

private void button1_Click(object sender, EventArgs e)
{
    if (comboBox1.Visible)
    {
        comboBox1.Visible = false;
        textBox1.Visible = true;
    }
    else
    {
        comboBox1.Visible = true;
        textBox1.Visible = false;
    }
}

The button click handler simply toggles the visibility of the two controls.

Question 2

private void button2_Click(object sender, EventArgs e)
{
    Form1 form = new Form1();
    form.ShowDialog();
}

This time the button handler instantiates a new form an then shows it as a modal dialog. Call Show() if you don't want to show modally.