Question

The problem is that the messagebox with “sure you wanna close?” does pop up, but when I click “no”, it still proceeds to close the program. Any suggestions?
Here’s my code:

    protected override void OnFormClosing(FormClosingEventArgs e)
    {
        CloseCancel();
    }

    public static void CloseCancel()
    {
        const string message = "Are you sure that you would like to cancel the installer?";
        const string caption = "Cancel Installer";
        var result = MessageBox.Show(message, caption,
                                     MessageBoxButtons.YesNo,
                                     MessageBoxIcon.Question);

        if (result == DialogResult.Yes)
            Environment.Exit(0);
    }

Answer 1

You are expected to set the Cancel property of the FormClosingEventArgs argument to true when you require the close-operation to be cancelled. And an explicit Environment.Exit(0) is normally not required since the form is on its way to being closed any way (the cancellation of the shutdown process is opt-in, not opt-out).

Replace the last bit with:

var result = MessageBox.Show(message, caption,
                             MessageBoxButtons.YesNo,
                             MessageBoxIcon.Question);

e.Cancel = (result == DialogResult.No);