Facing Error : Failed to Convert Value from bitmap to a byte[]

private void Upload_Click_1(object sender, EventArgs e)
        {
            OpenFileDialog open = new OpenFileDialog();
            //img filter
            open.Filter = "ImageFiles(*.jpg; *.jpeg; *.gif; *.bmp;)|*.jpg; *.jpeg; *.gif; *.bmp";
            if (open.ShowDialog() == DialogResult.OK)
            {
                String photoFilePath = open.FileName.ToString();
                pic.ImageLocation = photoFilePath;
                textbox.Text = photoFilePath;
            }
        }
        private void Save_Click(object sender, EventArgs e)
        {

         try
         {
             
             byte[] imageBt = null;
             FileStream fs = new FileStream(this.textbox.Text, FileMode.Open, FileAccess.Read);
             BinaryReader br = new BinaryReader(fs);
             imageBt = br.ReadBytes((int)fs.Length);
             
                String connString = ConfigurationManager.ConnectionStrings["logindb"].ConnectionString;
                SqlConnection conn = new SqlConnection(connString);
                SqlCommand cmd = new SqlCommand("storeimg", conn);
                //parameters
                cmd.Parameters.Add("@Photo", SqlDbType.Image).Value = pic.Image;
                cmd.Parameters.Add("@ID", SqlDbType.Int).Value = IDtex.Text;
                conn.Open();
                cmd.ExecuteNonQuery();
                conn.Close();
                MessageBox.Show("Added");
            }
            catch (Exception ex)
            {
                MessageBox.Show("Error" + ex.Message);
            }

        }