namespace By_paas
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void SetToZero(ref int number)
        {
            number = 0;
        }
        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {
            int x = 99, y = 100, z = 101;

            outputListBox.Items.Clear();
            outputListBox.Items.Add("x is set to" + x);
            outputListBox.Items.Add("y is set to" + y);
            outputListBox.Items.Add("z is set to" + z);

            SetToZero(ref x);
            SetToZero(ref y);
            SetToZero(ref z);

            outputListBox.Items.Add("-----------------------------------");
            outputListBox.Items.Add("x is set to" + x);
            outputListBox.Items.Add("y is set to" + y);
            outputListBox.Items.Add("z is set to" + z);
        }
    }
}