connectivity of c#.net forms with ms-acess

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 Insert_update_delete_navigate
{
  public partial class Form1 : Form
  {
   
  string ConnectionString = ("Provider = Microsoft.Jet.OLEDB.4.0; Data Source =  C:\\Documents and Settings\\Pintu\\Desktop\\Insert update delete navigate\\bin\\emp.mdb");
   
  OleDbCommand com;
  OleDbDataAdapter oledbda;
  string str;
  DataSet ds;
  byte flag;
  BindingManagerBase bm;

  public Form1()
  {
  InitializeComponent();
  }

  private void Form1_Load(object sender, EventArgs e)
  {
  OleDbConnection con = new OleDbConnection(ConnectionString);
  con.Open();
  str = "select * from student";
  com = new OleDbCommand(str, con);
  oledbda = new OleDbDataAdapter(com);
  ds = new DataSet();
  oledbda.Fill(ds, "student");
  textBox1.DataBindings.Add("Text", ds, "student.id");
  textBox2.DataBindings.Add("Text", ds, "student.name");
  bm = this.BindingContext[ds, "student"];
  con.Close();
  bindgrid();
  }

  private void bindgrid()
  {
  OleDbConnection con = new OleDbConnection(ConnectionString);
  con.Open();
  str = "select * from student";
  com = new OleDbCommand(str, con);
  oledbda = new OleDbDataAdapter(com);
  ds = new DataSet();
  oledbda.Fill(ds, "student");
  dataGridView1.DataMember = "student";
  dataGridView1.DataSource = ds;
  con.Close();

  }

  private void btn_first_Click(object sender, EventArgs e)
  {
  bm.Position = 0;
  }

  private void btn_next_Click(object sender, EventArgs e)
  {
  bm.Position += 1;
  }

  private void btn_previous_Click(object sender, EventArgs e)
  {
  bm.Position -= 1;
  }

  private void btn_last_Click(object sender, EventArgs e)
  {
  bm.Position = bm.Count - 1;
  }

  private void btn_add_Click(object sender, EventArgs e)
  {
  textBox1.Text = "";
  textBox2.Text = "";
  textBox1.Focus();
  flag = 1;
  }

  private void btn_modify_Click(object sender, EventArgs e)
  {
  flag = 2;
  }

  private void btn_save_Click(object sender, EventArgs e)
  {
  if (flag == 1)
  {
  OleDbConnection con = new OleDbConnection(ConnectionString);
  con.Open();
  str = "insert into student(id,name) values (@id,@name)";
  com = new OleDbCommand(str, con);
  com.Parameters.AddWithValue("@sid", textBox1.Text);
  com.Parameters.AddWithValue("@sname", textBox2.Text);
  com.ExecuteNonQuery();
  con.Close();
  MessageBox.Show("Records Successfuly Inserted");
  bindgrid();
  }

  if (flag == 2)
  {
  OleDbConnection con = new OleDbConnection(ConnectionString);
  con.Open();
  str = "update student set name='" + textBox2.Text.Trim() + "' where id='" + textBox1.Text.Trim() + "'";
  com = new OleDbCommand(str, con);
  com.ExecuteNonQuery();
  con.Close();
  MessageBox.Show("Records Successfuly Updated");
  bindgrid();
  }
  }

  private void btn_delete_Click(object sender, EventArgs e)
  {

  DialogResult result;
  result = MessageBox.Show("Are You sure want to Delete?", "Conformation", MessageBoxButtons.YesNo);
  if (result == System.Windows.Forms.DialogResult.Yes)
  {
  OleDbConnection con = new OleDbConnection(ConnectionString);
  str = "delete from student where id=@id";
  com = new OleDbCommand(str, con);
  com.Parameters.AddWithValue("@id", textBox1.Text);
  con.Open();
  com.ExecuteNonQuery();
  con.Close();
  MessageBox.Show("Records Successfuly Deleted");
  bindgrid();
   
  }
  else
  {
  MessageBox.Show("No action");
  }
   
  }
  }
}