Get value from another form in already opened form1

Question

My code work...problem is ...

Form 1 button click open Form2 and find value, when return value open new form not existing? Some help

I think it is problem line 11..12...

 

//form1:
 public partial class Form1 : Form
    {
        Form2 f2;
        public Form1()
        {
            InitializeComponent();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            if (f2 == null)
                f2 = new Form2();
            f2.ValueFromForm1(textBox1.Text);
            f2.Show();
        }
    }
//form2:
 public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }
        public void ValueFromForm1(string value)
        {
            textBox1.Text = value;
        }
    }