Windows Form如何将null返回到picturebox

UserControl1

的UserControl1

public void showpictures()
{
    {
        SqlConnection conn = new SqlConnection("Data Source=BRAIANX-PC;Initial Catalog=teste;Integrated Security=True");

            SqlCommand comand = new SqlCommand("select photto2 from dbo.tblProduct",conn);
            conn.Open();                    
            SqlDataReader reader = comand.ExecuteReader();

            Image imagem = null;
            if (reader.Read())
            {
                byte[] foto = (byte[])reader["photto2"];

                MemoryStream ms = new MemoryStream(foto);
                imagem = Image.FromStream(ms);
            }
            pictureBox1.Image = imagem;               
    }
}
public void show