ช่วยหน่อยครับ โค๊ดติดบั๊ก Incorrect syntax near '('.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.Sql;
using System.Data.SqlClient;

namespace Shop
{
    public partial class FormEditProduct : Form
    {
        
        public FormEditProduct()
        {
            InitializeComponent();
        }

        DataSet ds = new DataSet();
        SqlConnection con = new SqlConnection("server=REDARMY-LAPTOP;initial catalog=db_shop;user=sa;password=1234");
        SqlDataAdapter da = new SqlDataAdapter();
        BindingSource tbproduct = new BindingSource();

        private void button1_Click(object sender, EventArgs e)
        {
            int x;
            da.UpdateCommand = new SqlCommand("Update tb_product(name_prd, ref_id_type, detail_prd, price_prd) SET name_prd=@name_prd,ref_id_type=@ref_id_type,detail_prd=@detail_prd,price_prd=@price_prd",con);
            da.UpdateCommand.Parameters.AddWithValue("@name_prd",SqlDbType.NChar).Value = textBox1.Text;
            da.UpdateCommand.Parameters.AddWithValue("@ref_id_type", SqlDbType.Int).Value = comboBox1.SelectedValue;
            da.UpdateCommand.Parameters.AddWithValue("@detail_prd", SqlDbType.Text).Value = textBox2.Text;
            da.UpdateCommand.Parameters.AddWithValue("@price_prd", SqlDbType.Int).Value = textBox3.Text;
            da.UpdateCommand.Parameters.AddWithValue("@id_prd", SqlDbType.Int).Value = ds.Tables[0].Rows[tbproduct.Position][0];

            con.Open();
            x = da.UpdateCommand.ExecuteNonQuery();
            con.Close();
            if(x >= 1)         
                MessageBox.Show("Record is Update");
            
        }

        private void button2_Click(object sender, EventArgs e)
        {
            da.SelectCommand = new SqlCommand("select * from tb_product",con);
            ds.Clear();
            da.Fill(ds);
            dg.DataSource = ds.Tables[0];

            tbproduct.DataSource = ds.Tables[0];
            textBox1.DataBindings.Add(new Binding("text", tbproduct, "name_prd"));
            comboBox1.DataBindings.Add(new Binding("text", tbproduct, "ref_id_type"));
            textBox2.DataBindings.Add(new Binding("text", tbproduct, "detail_prd"));
            textBox3.DataBindings.Add(new Binding("text", tbproduct, "price_prd"));
        }

        private void FormEditProduct_Load(object sender, EventArgs e)
        {

        }

        private void button3_Click(object sender, EventArgs e)
        {
            tbproduct.MovePrevious();
            dgUpdate();
        }

        private void button4_Click(object sender, EventArgs e)
        {
            tbproduct.MoveNext();
            dgUpdate();
        }
        private void dgUpdate() 
        {
            dg.ClearSelection();
            dg.Rows[tbproduct.Position].Selected = true;
        }
    }
}