VC# ทำไมเวลาเราInsert intoข้อมูลลงฐานข้อมูลเวลารันในโปรเจคมันถึงไม่ได้ล่ะครับ

String Con = "Data Source=.\\SQLEXPRESS;AttachDbFilename=|DataDirectory|"
                     + "\\TCTSuperMarket.mdf;Integrated Security=True;User Instance=True";

private void btsave_Click(object sender, EventArgs e)
        {
            if (txtProID.Text == "" || txtproname.Text == "" || txtdetailpro.Text == "" ||
                txtnuminventory.Text == "" || txtcost.Text == "" || txtprice.Text == "")
            {
                MessageBox.Show("กรุณากรอกข้อมูลให้ครบถ้วน", "คำเตือน", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
                txtProID.Focus();
            }
            else
            {
            SqlConnection Conn = new SqlConnection(Con);
            SqlCommand cmd = new SqlCommand("INSERT INTO Product(ProID,ProName,Detail,NumInventory,Cost,Price)" +
                   " values(@ProID,@ProName,@Detail,@NumInventory,@Cost,@Price)", Conn);
            cmd.Parameters.AddWithValue("@ProID", txtProID.Text);
            cmd.Parameters.AddWithValue("@ProName", txtproname.Text);
            cmd.Parameters.AddWithValue("@Detail", txtdetailpro.Text);
            cmd.Parameters.AddWithValue("@NumInventory", txtnuminventory.Text);
            cmd.Parameters.AddWithValue("@Cost", txtcost.Text);
            cmd.Parameters.AddWithValue("@Price", txtprice.Text);
            try
            {
                Conn.Open();
                cmd.ExecuteNonQuery();
                ShowData();
                MessageBox.Show("ทำการบันทึกข้อมูลเรียบร้อย", "ยืนยันการบันทึกข้อมูล", MessageBoxButtons.OK, MessageBoxIcon.Information);
                txtProID.Text = "";
                txtproname.Text = "";
                txtdetailpro.Text = "";
                txtnuminventory.Text = "";
                txtcost.Text = "";
                txtprice.Text = "";
                Conn.Close();
            }
            catch (Exception)
            {
                MessageBox.Show("Error!!");
            }
            
        }
        }

 public void ShowData()
        {
            using (SqlConnection Conn = new SqlConnection(Con))
            {
                Conn.Open();
                SqlCommand cmd = new SqlCommand("SELECT * FROM Product", Conn);
                DataTable dt = new DataTable();
                SqlDataAdapter da = new SqlDataAdapter(cmd);
                da.Fill(dt);
                datagridproduct.DataSource = dt;
                Conn.Close();
            }
        }