使用C#语言绘制折线图

使用C#语言绘制一个网格，使得X,Y轴都可以拖动，数据在网格上对应，然后描点连线绘制折线图，数据点较多，且数值跨度较大有正有负，这种情况该怎么写代码，
我写的这段代码绘制的网格不是封闭图形该怎么修改

    public float move = 10f;
    public float newX = 1000f;
    public float newY = 400F;
    private PointF[] pointList;
    int Row = 20;
    int colums = 10;

public void DrawXYAxis(Graphics g)
{
//绘制X轴,
PointF px1 = new PointF(move, 200f);
PointF px2 = new PointF(newX, 200f);
g.DrawLine(new Pen(Brushes.Black, 2), px1, px2);
for (int i = 0; i < Row; i++)
{
g.DrawLine(new Pen(Color.Black), (i + 1) * 1000 / Row, move, (i + 1) * 1000 / Row, 400);
}
//绘制Y轴
PointF py1 = new PointF(move, move);
PointF py2 = new PointF(move, newY);
g.DrawLine(new Pen(Brushes.Black, 2), py1, py2);
for (int i = 0; i < colums; i++)
{
g.DrawLine(new Pen(Color.Black), move, (i + 1) * 400 / colums, 1000, (i + 1) * 400 / colums);
}
}