How to Edit / Delete Data using Datagridview in .NET?

using System.Data;
using System.Data.SqlClient;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        DataTable dt = new DataTable();
        DataRow dr;
        int rindex;

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            dt.Columns.Add("eno");
            dt.Columns.Add("empname");
            dt.Columns.Add("sal");

            dr = dt.NewRow();
            dr["eno"] = "101";
            dr["empname"] = "Ravindran";
            dr["sal"] = "45000";
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr["eno"] = "102";
            dr["empname"] = "Mike";
            dr["sal"] = "25000";
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr["eno"] = "103";
            dr["empname"] = "James";
            dr["sal"] = "33000";
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr["eno"] = "104";
            dr["empname"] = "Allen";
            dr["sal"] = "45000";
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr["eno"] = "105";
            dr["empname"] = "Andrew";
            dr["sal"] = "18000";
            dt.Rows.Add(dr);

            dt.AcceptChanges();
            dataGridView1.DataSource = dt;
        }

        private void btnDelete_Click(object sender, EventArgs e)
        {
            string eno = dataGridView1.Rows[rindex].Cells[0].Value.ToString();
            //using eno to delete records from database table
        }

        private void btnModify_Click(object sender, EventArgs e)
        {
            DataTable dtmod = new DataTable();

            //here we can lod only modifed data rows in the new data table
            dtmod = dt.GetChanges();

            for (int i = 0; i <= dtmod.Rows.Count - 1; i++)
            {
                //here you can get updated row details and update in sql server database
            }
        }

        private void dataGridView1_RowEnter(object sender, DataGridViewCellEventArgs e)
        {
            rindex = e.RowIndex;
        }
    }
}