ช่วยด้วยครับต้องแสดงค่าใน datagridview windows form application

private void button1_Click(object sender, EventArgs e)
{
CN.Open();
string SQL = "Insert into tblProduct Values (" + textBox6.Text + "," + textBox5.Text + "," + textBox4.Text + ",'" + textBox8.Text + "'" + ")";
SqlCommand CM = new SqlCommand(SQL, CN);
CM.ExecuteNonQuery(); 

LoadGridview() ; //โหลดข้อมูลกลับขึ้นมา
}

  private void LoadGridview() {

            try
            {
                string strConnString = "Server=localhost;UID=sa;PASSWORD=sa123456;database=NORTHWND;Max Pool Size=400;Connect Timeout=600;";
                string strSQL = "select ProductID,ProductName,UnitPrice,UnitsInStock from Products";
                using (SqlConnection conn = new SqlConnection(strConnString))
                {
                    conn.Open();
                    using (SqlCommand cmd = new SqlCommand(strSQL,conn))
                    {
                        using (SqlDataAdapter adapter = new SqlDataAdapter(cmd))
                        {
                            DataSet ds = new DataSet();
                            adapter.Fill(ds, "product");
                            dataGridView1.DataSource = ds.Tables[0];
                        }
                    }
                }
              
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }