C# ช่วยด้วยครับ จะอัพโหลดไฟล์ pdf ไปใส่ตารางยังไง ..

private void dataGridViewcus_CellContentClick(object sender, DataGridViewCellEventArgs e)
        {
            if (e.ColumnIndex == 5)

                System.Diagnostics.Process.Start("" + dataGridViewcus[5, e.RowIndex].Value);

  private void btnอัพโหลด_Click(object sender, EventArgs e)
        {
            ofd.Filter = "PDF |*.pdf";
            if (ofd.ShowDialog()==DialogResult.OK)
            {
                txt_11.Text = ofd.SafeFileName;
                
            }

private void dataGridViewcus_CellContentClick(object sender, DataGridViewCellEventArgs e)
        {
            if (e.ColumnIndex == 5)

                System.Diagnostics.Process.Start("" + dataGridViewcus[5, e.RowIndex].Value);

  private void btnอัพโหลด_Click(object sender, EventArgs e)
        {
            ofd.Filter = "PDF |*.pdf";
            if (ofd.ShowDialog()==DialogResult.OK)
            {
                txt_11.Text = ofd.SafeFileName;
                
            }

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

namespace Project_cs
{
    public partial class ข้อมูลลูกค้า : Form
    {
        public ข้อมูลลูกค้า()
        {
            InitializeComponent();
        }
        SqlConnection cus = new SqlConnection("Server=DESKTOP-35EE4RH\\SQLEXPRESS; Database=Projectcs; Trusted_Connection=True;");
        private void ข้อมูลลูกค้า_Load(object sender, EventArgs e)
        {


            try
            {
                cus.Open();
                Showdata();

                dataGridViewcus.RowsDefaultCellStyle.BackColor = Color.White;
                dataGridViewcus.AlternatingRowsDefaultCellStyle.BackColor = Color.PowderBlue;

            }
            catch
            {
                MessageBox.Show("Error");
            }
        }
            private void Showdata()
        {
            string sql = "SELECT * FROM Table_cus3";
            SqlCommand com = new SqlCommand(sql, cus);
            SqlDataReader dr = com.ExecuteReader();
            DataTable tb = new DataTable();
            if (dr.HasRows)
            {
                tb.Load(dr);
                dataGridViewcus.DataSource = tb;

            }
            else
            {
                dataGridViewcus.DataSource = null;

            }
            dr.Close();
        }
        private void Cleardata()
        {
          
        }

        private void btnsave1_Click(object sender, EventArgs e)
        {
            string sql = "INSERT INTO Table_cus3(cus_id,cus_name,cus_date,cus_address,cus_pdf) VALUES ('" + txtcusid.Text.Trim() + "','" + txtcusname.Text.Trim() + "','" + dateTimePickercus.Text.Trim() +  "','" + txtcusadd.Text.Trim() + "','" + txt_11.Text.Trim() + "')";
            SqlCommand com = new SqlCommand(sql, cus);
            com.ExecuteNonQuery();
            MessageBox.Show("บันทึกเรียบร้อยแล้ว");
            Showdata();
            Cleardata();

        }

        private void btnลบ_Click(object sender, EventArgs e)
        {
            if (txtcusid.Text.Trim() == "") { MessageBox.Show("กรุณาเลือกข้อมูล"); return; }
            if (MessageBox.Show("คุณต้องการลบข้อมูลใช่หรือไม่ !!!", "คำยืนยัน", MessageBoxButtons.YesNo, MessageBoxIcon.Question) == System.Windows.Forms.DialogResult.Yes)
            {
                String sql = "DELETE FROM Table_cus3 WHERE cus_id='" + txtcusid.Text.Trim() + "'";
                SqlCommand com = new SqlCommand(sql, cus);
                com.ExecuteNonQuery();
                MessageBox.Show("ลบข้อมูลเรียบร้อยแล้ว");
                Showdata();
                Cleardata();
            }
        }

        private void dataGridViewcus_CellContentClick(object sender, DataGridViewCellEventArgs e)
        {
            if (e.ColumnIndex == 4 && System.IO.File.Exists("" + dataGridViewcus[4, e.RowIndex].Value))

                System.Diagnostics.Process.Start("" + dataGridViewcus[4, e.RowIndex].Value);

        }

        OpenFileDialog ofd = new OpenFileDialog();
        

        private void btnอัพโหลด_Click(object sender, EventArgs e)
        {
            ofd.Filter = "PDF |*.pdf";
            if (ofd.ShowDialog()==DialogResult.OK)
            {
                txt_11.Text = ofd.SafeFileName;
                
            }
        }

        private void groupBox1_Enter(object sender, EventArgs e)
        {

        }

        private void txt_11_TextChanged(object sender, EventArgs e)
        {

        }

        private void dataGridViewcus_CellMouseDoubleClick(object sender, DataGridViewCellMouseEventArgs e)
        {
            if (e.RowIndex == -1) { return; }
            txtcusid.Text = dataGridViewcus.Rows[e.RowIndex].Cells[0].Value.ToString();
            txtcusname.Text = dataGridViewcus.Rows[e.RowIndex].Cells[1].Value.ToString();
            dateTimePickercus.Text = dataGridViewcus.Rows[e.RowIndex].Cells[2].Value.ToString();
            txtcusadd.Text = dataGridViewcus.Rows[e.RowIndex].Cells[3].Value.ToString();
            txt_11.Text = dataGridViewcus.Rows[e.RowIndex].Cells[4].Value.ToString();
        }

        private void fileSystemWatcher1_Changed(object sender, System.IO.FileSystemEventArgs e)
        {

        }
    }
    }