DataGridView显示行号

   DataGridView默认的属性中，不可设置显示行号。
   效果如下：
 
为了表示行号，我们可以在DataGridView的RowPostPaint事件中进行绘制。
RowPostPaint事件，具体可以参照MSDN。
下面是实现代码：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Drawing.Imaging;
using System.Text;
using System.Windows.Forms;

namespace DrawRowIndex
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void Form1_Load(object sender, EventArgs e)
        {
            dataGridView1.Dock = DockStyle.Fill;
            dataGridView1.DataSource = ImageCodecInfo.GetImageDecoders();
        }
        private void dataGridView1_RowPostPaint(object sender, DataGridViewRowPostPaintEventArgs e)
        {
            Rectangle rectangle = new Rectangle(e.RowBounds.Location.X,
                e.RowBounds.Location.Y,
                dataGridView1.RowHeadersWidth - 4,
                e.RowBounds.Height);

            TextRenderer.DrawText(e.Graphics, (e.RowIndex + 1).ToString(),
                dataGridView1.RowHeadersDefaultCellStyle.Font, rectangle,
                dataGridView1.RowHeadersDefaultCellStyle.ForeColor,
                TextFormatFlags.VerticalCenter | TextFormatFlags.Right);
        }
    }
}