SaveFileDialog in C#

Question

hi friends,How are you?

Today i want to know.....
how to use SaveFileDialog to save an image from windows form Application. I tried below code but there should be something wrong.
(i have an image on form in picturebox)

private void button2_Click(object sender, EventArgs e)

        {

            saveFileDialog1.ShowDialog();

        }

        private void saveFileDialog1_FileOk(object sender, CancelEventArgs e)

        {

            string name = saveFileDialog1.FileName;

            File.WriteAllText(name,pictureBox1.Image.ToString());

        }