c# ขอคำแนะนำในการ Call function ระหว่างฟอร์มหน่อยครับ

namespace CallFunction
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        public void CallFunction()
        {
           MessageBox.Show("Test Call Function.");
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {
            Form2 f2 = new Form2(this);
            f2.Show();
        }
    }
}

namespace CallFunction
{
    public partial class Form2 : Form
    {
        public   Form1 f1;

        public Form2(Form1 f )
        {
            InitializeComponent();
            f1 = f
        }

        private void button1_Click(object sender, EventArgs e)
        {
            f1.CallFunction();
        }
    }
}