Getting data in Datagridvw in buttnclick but unable 2 update

thanks Satyapriya Nayak for your quick reply 

i think i have asked only half a question 

kindly see my changed question and help me if you can

thanks

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.OleDb;

namespace Update_delete_datagridview
{
    public partial class Form1 : Form
    {
       OleDbDataAdapter oledbda;
       OleDbCommandBuilder olcb;
       DataTable dataTable;
       BindingSource bindingSource;
       string ConnectionString = System.Configuration.ConfigurationSettings.AppSettings["dsn"];
       string str;

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {

            OleDbConnection con = new OleDbConnection(ConnectionString);
            con.Open();
            str = "SELECT * FROM student";
         
            oledbda = new OleDbDataAdapter(str, con);
            olcb = new OleDbCommandBuilder(oledbda);
            dataTable = new DataTable();
            oledbda.Fill(dataTable);
            con.Close();
            bindingSource = new BindingSource();
            bindingSource.DataSource = dataTable;
            dataGridView1.DataSource = bindingSource;
            dataGridView1.Columns[0].Visible = false;
        }

        private void btnaddupdate_Click(object sender, EventArgs e)
        {
            try
            {
                oledbda.Update(dataTable);
            }
            catch (Exception exceptionObj)
            {
                MessageBox.Show(exceptionObj.Message.ToString());
            }
            MessageBox.Show("Records updated");

        }

        private void btndelete_Click(object sender, EventArgs e)
        {
            try
            {
                dataGridView1.Rows.RemoveAt(dataGridView1.CurrentRow.Index);
                oledbda.Update(dataTable);
            }
            catch (Exception exceptionObj)
            {
                MessageBox.Show(exceptionObj.Message.ToString());
            }
            MessageBox.Show("Records Deleted");
        }

      
    }
}