how to code for an eraser in paint...

FillEraser in picture box mouse move event

private void FillEraser(object sender, MouseEventArgs e)
{
if (pctFundusMain.Image != null)
{
if (e.Button == MouseButtons.Left)
{
PictureBox thisform = (PictureBox)sender;
Graphics g = thisform.CreateGraphics();
var pen = new Pen(Color.White, 5);
pen.Width = FixEraserThickness();
// new SolidBrush(Color.White);
_bitmap = new Bitmap(pctFundusMain.Image);
g = Graphics.FromImage(_bitmap);
var cursorLocation = new Point(e.X + 5, e.Y + 5);
// g.DrawLine(pen, e.X, e.Y, e.X + 5, e.Y + 5);
g.DrawLine(pen, pe, cursorLocation);
pctFundusMain.Image = _bitmap;
pe = cursorLocation;
}
}
}