ขอสอบถามเกี่ยวกับการ Update ข้อมูล ใน Gridview ด้วย Checkbox

private void btnedit_Click(object sender, EventArgs e)
        {

                    edit_subdept form = new edit_subdept();
                    if (form.ShowDialog() == DialogResult.OK)
                    {
                        showdgvmain();
                    }
                    
        }

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

namespace ProgramHR
{
    public partial class edit_subdept : Form
    {
        public edit_subdept()
        {
            InitializeComponent();
            connect_db.Connect();
        }
        public string party_ID { get; set; }

        private void btnclosesubdept_Click(object sender, EventArgs e)
        {
            this.Close();
        }
        DataTable dt = new DataTable();

        private void edit_subdept_Load(object sender, EventArgs e)
        {
            string sql = "SELECT party_name FROM tbl_Party WHERE party_ID = '" + party_ID + "'";
          connect_db.ExcuteData(sql);

            if (dt.Rows.Count > 0)
            {
                this.txtsubdeptname.Text = dt.Rows[0]["party_name"].ToString();

            }

            dt = null;
        }

        private void btneditsubdept_Click(object sender, EventArgs e)
        {

            if (string.IsNullOrEmpty(this.txtsubdeptname.Text))
            {
                MessageBox.Show("Please input (party_name)");
                this.txtsubdeptname.Focus();
                return;
            }

            string sql = "UPDATE tbl_Party SET party_name ='" + this.txtsubdeptname.Text + "' WHERE party_ID = '" + party_ID + "' ";
            connect_db.ExcuteData(sql);
            MessageBox.Show("ระบบได้แก้ไขข้อมูลเรียบร้อย", "", MessageBoxButtons.OK, MessageBoxIcon.Information);
            this.DialogResult = DialogResult.OK;
        }
       
    }
            
}