How to get First,Last,Next,Previews Data in .Net C#

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Data.Odbc;
using System.IO;
namespace WindowsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        OdbcDataAdapter da;
        DataSet ds;
        int i = 0;
        int j;
        OdbcConnection conn;
        int last;
        private void Form1_Load(object sender, EventArgs e)
        {
            conn = new OdbcConnection("dsn=t1");
            conn.Open();
            da = new OdbcDataAdapter("select * from emp", conn);
            OdbcCommandBuilder builder = new OdbcCommandBuilder(da);
            ds = new DataSet();
            da.Fill(ds, "emp");
            dataGridView1.DataSource = ds.Tables["emp"];
        }

        private void btnfirst_Click(object sender, EventArgs e)
        {
            if (ds.Tables[0].Rows.Count > 0)
            {
                i = 0;
                textBox1.Text = ds.Tables[0].Rows[i]["ID"].ToString();
                textBox2.Text = ds.Tables[0].Rows[i]["empname"].ToString();
                textBox3.Text = ds.Tables[0].Rows[i]["salary"].ToString();
            }
        }
        private void btnlast_Click(object sender, EventArgs e)
        {
            i = ds.Tables[0].Rows.Count - 1;
            textBox1.Text = ds.Tables[0].Rows[i]["ID"].ToString();
            textBox2.Text = ds.Tables[0].Rows[i]["empname"].ToString();
            textBox3.Text = ds.Tables[0].Rows[i]["salary"].ToString();

        }
        private void btnnext_Click(object sender, EventArgs e)
        {

            if (i < ds.Tables[0].Rows.Count - 1)
            {
                i++;
                textBox1.Text = ds.Tables[0].Rows[i]["ID"].ToString();
                textBox2.Text = ds.Tables[0].Rows[i]["empname"].ToString();
                textBox3.Text = ds.Tables[0].Rows[i]["salary"].ToString();
            }
            else
            {
            }
        }
        private void btnprevious_Click(object sender, EventArgs e)
        {
            if (i == ds.Tables[0].Rows.Count - 1 || i != 0)
            {
                i--;
                textBox1.Text = ds.Tables[0].Rows[i]["ID"].ToString();
                textBox2.Text = ds.Tables[0].Rows[i]["empname"].ToString();
                textBox3.Text = ds.Tables[0].Rows[i]["salary"].ToString();
            }
            else
            {
            }
        }
    }
}

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