To insert / displayRow number in DataGridView

Add following code to the event dataGridView1_RowPostPaint in your Code behind

private void dataGridView1_RowPostPaint(object sender, DataGridViewRowPostPaintEventArgs e)
{
// get the row number in leading zero format,
// where the width of the number = the width of the maximum number
int RowNumWidth = dataGridView1.RowCount.ToString().Length;
StringBuilder RowNumber = new StringBuilder(RowNumWidth);
RowNumber.Append(e.RowIndex + 1);
while (RowNumber.Length < RowNumWidth)
RowNumber.Insert(0, "0");
// get the size of the row number string
SizeF Sz = e.Graphics.MeasureString(RowNumber.ToString(), this.Font);
// adjust the width of the column that contains the row header cells
if (dataGridView1.RowHeadersWidth < (int)(Sz.Width + 20))
dataGridView1.RowHeadersWidth = (int)(Sz.Width + 20);
// draw the row number
e.Graphics.DrawString(
RowNumber.ToString(),
this.Font,
SystemBrushes.ControlText,
e.RowBounds.Location.X + 15,
e.RowBounds.Location.Y + ((e.RowBounds.Height - Sz.Height) / 2));
}