how to draw a coordinated grid in c#.........please answer my question

private void Form1_Paint(object sender, PaintEventArgs e)
{
Graphics g = e.Graphics;
Pen p = new Pen(Color.White);

g.FillRectangle(Brushes.HotPink, 30, 30, 30, 30);


for (int i = 0; i <= num_of_cells; i++) //to make a 20X20 grid
{
g.DrawLine(p, i *cell_size, 0, i *cell_size, num_of_cells *cell_size); //for horizontal lines


g.DrawLine(p, 0, i *cell_size, num_of_cells *cell_size, i *cell_size); //for vertical lines


}
g.Dispose();

}

i am drawing grid using for loop and drawline method.........but now i don't find any way to assign coordinates to each small square of grid.