C#

Form1

<code>
 public delegate void TestDelegate(int i);
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Form2 frmOpen = new Form2();            
            frmOpen.ShowDialog();
        }
        public void GetValueA(int i)
        {
            textBox1.Text = i.ToString();         
        }
    }
</code>

Form2
<code>
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            int b;
            b = Convert.ToInt32(textBox1.Text);
            
            Form1 frm1=new Form1();
            TestDelegate td = new TestDelegate(frm1.GetValueA);
            td(b);
            Close();
        }
    }
</code>