Question

im developing windows application using c#. i want to close the application and show new form after clicking the button, i did it, but every time i cliecked the button, it shows the another windows and when i going to task manager that form isntance still running. i want avoid that. i am using this.close() function to exit from the form.

Answer 1

Let’s suppose you have Form1 and Form2.

The code in Form1 should be something like this:

public partial class Form1 : Form
{
    private Form2 _form2;

    public Form1()
    {
        InitializeComponent();
        _form2 = new Form2();
        _form2.VisibleChanged += new EventHandler(_form2_VisibleChanged);
    }

    void _form2_VisibleChanged(object sender, EventArgs e)
    {
        if (!_form2.Visible)
            Show();
    }

    private void Form1_FormClosing(object sender, FormClosingEventArgs e)
    {
        e.Cancel = true;
        this.Hide();
        _form2.Show();
    }
}

And in Form2 all you need to do is:

private void Form2_FormClosing(object sender, FormClosingEventArgs e)
{
    e.Cancel = true;
    Hide();
}

Of course, you must suscribe to the event FormClosing in Form2, but if you do it through the designer (Form Properties, clicking on Events icon) just paste those two lines inside the method it creates)

What is this code doing?

In Form1:

• Create a instance of Form2
• In Form1_FormClosing method, all we do is hide the form instead of closing it when the user closes it, and showing the instance of Form2
• Suscribe to the VisibleChanged event
• When the event fires, if the instance of Form2 isn’t visible, then Form1 appears.

In Form2:

• The 2nd of the above steps, but without showing anything.

If you want to do it when you click on a button, all you need to do is do the same but on the Click event on the button instead of the FormClosing event.