Inserting & Retrieving records from M.S.Excel-2007 using oledb in C#.net

using System;
using System.Data;
using System.Data.OleDb;
using System.Windows.Forms;
using Microsoft.VisualBasic;

namespace xloledb07
{
    public partial class Form1 : Form
    {
        OleDbConnection con;
        OleDbCommand cmd;
        OleDbDataAdapter da;
        DataSet ds;
        int rno = 0;

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            con = new OleDbConnection(@"provider=microsoft.ace.oledb.12.0;data source=e:\prash\xldb.xlsx;extended properties=""excel 12.0;hdr=yes;"" ");
            loaddata();
            showdata();
        }

        void loaddata()
        {
            da = new OleDbDataAdapter("select * from [student$]", con);
            ds = new DataSet();
            da.Fill(ds, "student");
            ds.Tables[0].Constraints.Add("pk_sno", ds.Tables[0].Columns[0], true);
            dataGridView1.DataSource = ds.Tables[0];
        }

        void showdata()
        {
            textBox1.Text = ds.Tables[0].Rows[rno][0].ToString();
            textBox2.Text = ds.Tables[0].Rows[rno][1].ToString();
            textBox3.Text = ds.Tables[0].Rows[rno][2].ToString();
        }

        private void btnInsert_Click(object sender, EventArgs e)
        {
            cmd = new OleDbCommand("insert into [student$] values(" + textBox1.Text + ",' " + textBox2.Text + " ',' " + textBox3.Text + " ')", con);
            con.Open();
            int n = cmd.ExecuteNonQuery();
            con.Close();
            if (n > 0)
            {
                MessageBox.Show("record inserted");
                loaddata();
            }
            else
                MessageBox.Show("insertion failed");
        }

        private void btnSearch_Click(object sender, EventArgs e)
        {
            int n = Convert.ToInt32(Interaction.InputBox("Enter sno:", "Search", "20", 200, 200));
            DataRow drow = ds.Tables[0].Rows.Find(n);
            if (drow != null)
            {
                textBox1.Text = drow[0].ToString();
                textBox2.Text = drow[1].ToString();
                textBox3.Text = drow[2].ToString();
            }
            else
                MessageBox.Show("Record not found");
        }

        private void btnUpdate_Click(object sender, EventArgs e)
        {
            cmd = new OleDbCommand(" update [student$] set sname='" + textBox2.Text + "',course='" + textBox3.Text + "' where sno=" + textBox1.Text, con);
            con.Open();
            int n = cmd.ExecuteNonQuery();
            con.Close();
            if (n > 0)
            {
                MessageBox.Show("Record Updated");
                loaddata();
            }
            else
                MessageBox.Show("Update failed");
        }

        private void btnFirst_Click(object sender, EventArgs e)
        {
            if (ds.Tables[0].Rows.Count > 0)
            {
                rno = 0;
                showdata();
                MessageBox.Show("First Record");
            }
            else
                MessageBox.Show("no records");
        }

        private void btnPrevious_Click(object sender, EventArgs e)
        {
            if (ds.Tables[0].Rows.Count > 0)
            {
                if (rno > 0)
                {
                    rno--;
                    showdata();
                }
                else
                    MessageBox.Show("First Record");
            }
            else
                MessageBox.Show("no records");
        }

        private void btnNext_Click(object sender, EventArgs e)
        {
            if (ds.Tables[0].Rows.Count > 0)
            {
                if (rno < ds.Tables[0].Rows.Count - 1)
                {
                    rno++;
                    showdata();
                }
                else
                    MessageBox.Show("Last Record");
            }
            else
                MessageBox.Show("no records");
        }

        private void btnLast_Click(object sender, EventArgs e)
        {
            if (ds.Tables[0].Rows.Count > 0)
            {
                rno = ds.Tables[0].Rows.Count - 1;
                showdata();
                MessageBox.Show("Last Record");
            }
            else
                MessageBox.Show("no records");
        }

        private void btnClear_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox2.Text = textBox3.Text = "";
        }

        private void btnExit_Click(object sender, EventArgs e)
        {
            this.Close();
        }
    }
}

Note. The 'xldb.xlsx' file is provided in the xloledb07.zip file along with the source code.