How to troubleshoot update in c# datagridview

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C#

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 MySql.Data.MySqlClient;

namespace STIMKTIAA_Info
{
    public partial class frmUPMaintenances : Form
    {
        MySqlConnection con = new MySqlConnection();
        MySqlCommand cmd;
        MySqlCommandBuilder cdb;
        MySqlDataAdapter ad;
        DataSet ds;
        DataTable dt;
        
        
        public frmUPMaintenances()
        {
            InitializeComponent();
            cbxAccessType.Items.Add("ÄDMIN");
            cbxAccessType.Items.Add("STI ADMIN");
            cbxAccessType.Items.Add("ALUMNI");
        }

        private void frmUPMaintenances_Load(object sender, EventArgs e)
        {
            this.CancelButton = btnCancel;
        }

        private void btnLoad_Click(object sender, EventArgs e)
        {
            con.ConnectionString = ("datasource = localhost;port=3306; Initial Catalog = 'alumni_info'; username =root; password=");
            string q = "SELECT * FROM `user_login`";
            con.Open();
            cmd = new MySqlCommand(q, con);
            ad = new MySqlDataAdapter(cmd);
            cdb = new MySqlCommandBuilder(ad);
            ds = new DataSet();
            ad.Fill(ds, "user_login");
            dt = ds.Tables["user_login"];
            con.Close();
            //btnAdd.Visible = false;
            dataGridView1.DataSource = ds.Tables["user_login"];
            dataGridView1.SelectionMode = DataGridViewSelectionMode.FullRowSelect;

        }
             

        private void btnUpdate_Click(object sender, EventArgs e)
        {
            string q = "UPDATE `user_login` SET USER_ID ='"+ txtUID.Text +"', LNAME ='" + txtLName.Text + "', FNAME ='" + txtFName.Text + "', MNAME ='" + txtMI.Text + "', POSITION ='" + txtPosition.Text + "', ACCESS_TYPE='" + cbxAccessType.SelectedItem + "', UNAME ='" + txtUName.Text + "', PASSWORD ='" + txtPwd.Text + "'";
            ExecuteQuery(q);
            ad.Update(dt);
            btnDelete.Enabled = false;
            btnUpdate.Enabled = true;
            //btnAdd.Visible = false;
        }

       
        public void openCon()
        {
            if (con.State == ConnectionState.Closed)
            {
                con.Open();
            }
        }

        public void closeCon()
        {
            if (con.State == ConnectionState.Open)
            {
                con.Close();
            }
        }

        public void ExecuteQuery(string q)
        {
            try
            {
                con.Open();
                cmd = new MySqlCommand(q, con);
                if (cmd.ExecuteNonQuery() == 1)
                {
                    MessageBox.Show("Query EXECUTED!!");

                }
                else
                {
                    MessageBox.Show("Query UNSUCCESSFUL!");
                }
            }
            catch (Exception eh)
            {
                MessageBox.Show(eh.Message);
            }
            finally
            {
                con.Close();
            }

        }

        private void btnDelete_Click(object sender, EventArgs e)
        {
            string q = "DELETE FROM `user_login` WHERE USER_ID ='" + txtUID.Text + "'";
            ExecuteQuery(q);
            ad.Update(dt);
            txtLName.Text = " ";
            txtFName.Text = " ";
            txtMI.Text = " ";
            txtPosition.Text = " ";
            txtUName.Text = " ";
            txtPwd.Text = " ";
            //btnAdd.Visible = false;
        }

        private void btnClear_Click(object sender, EventArgs e)
        {
            txtUID.Clear();
            txtLName.Clear();
            txtFName.Clear();
            txtMI.Clear();
            txtPosition.Clear();
            txtUName.Clear();
            txtPwd.Clear();
            cbxAccessType.Items.Clear();
            //btnAdd.Visible = false;
        }

        private void btnCancel_Click(object sender, EventArgs e)
        {
            this.Close();
            frmMainPage mp = new frmMainPage();
            mp.Show();
            //btnAdd.Visible = false;
        }

        private void cbxAccessType_SelectedIndexChanged(object sender, EventArgs e)
        {
            cbxAccessType.Text = cbxAccessType.SelectedItem.ToString();
            string v;
            v = cbxAccessType.Text;
        }

        private void dataGridView1_CellContentClick(object sender, DataGridViewCellEventArgs e)
        {
           /* dataGridView1.DataSource = null;
            dataGridView1.Rows.Clear();
            dataGridView1.Refresh();*/
            DataGridViewRow dg = dataGridView1.SelectedRows[0];
            txtUID.Text = dg.Cells[0].Value.ToString();
            txtLName.Text = dg.Cells[1].Value.ToString();
            txtFName.Text = dg.Cells[2].Value.ToString();
            txtMI.Text = dg.Cells[3].Value.ToString();
            txtPosition.Text = dg.Cells[4].Value.ToString();
            cbxAccessType.SelectedText = dg.Cells[5].Value.ToString();
            txtUName.Text = dg.Cells[6].Value.ToString();
            txtPwd.Text = dg.Cells[7].Value.ToString();

        }


       

    }
}

this my code when the update button is on the loose all the data in datagridview changes to one particular item while access type column the data is missing

What I have tried:

I tried to rewrite the UPDATE sql command but it never runs again