c＃来自另一个类的MainForm图形被删除

Question

我想在另一个类的选项卡中的一个面板上绘制一些行，这些面板属于Form1 我试图传递Form1，面板参数，我可以绘制我想要的，但是当类绘制方法完成时，如果我从我的UI交换制表符，图纸就不见了......

Form1按钮;

private void button1_Click(object sender, EventArgs e)
    {
        panel1 = new Class1().Graph_set_axis(panel1);
    }

class1方法;

public Panel Graph_set_axis(Panel _local)
    {

        Pen pen = new Pen(Color.Black, 2);
        Point Origin = new Point(0, 0);
        Point A = new Point();
        Point B = new Point();
        Graphics G = _local.CreateGraphics();
        G.TranslateTransform(0, _local.Height);
        G.ScaleTransform(1.0F, -1.0F);

        A.X = 0;
        A.Y = _local.Height;
        B.X = _local.Width;
        B.Y = 0;
        G.DrawLine(pen, Origin, A);
        G.DrawLine(pen, Origin, B);

        int Y_units;
        int X_units;
        //    int i = 1;

        Y_units = _local.Height / 30;
        for (int i = 0; i * Y_units < _local.Height; i++)
        {
            A.X = 0;
            A.Y = i * Y_units;
            B.X = A.X + 5;
            B.Y = A.Y;
            G.DrawLine(pen, A, B);
        }

        X_units = _local.Width / 30;
        for (int i = 0; i * X_units < _local.Width; i++)
        {
            A.X = i * X_units;
            A.Y = 0;
            B.X = A.X;
            B.Y = A.Y + 5;
            G.DrawLine(pen, A, B);
        }

        return _local;
    }

我需要在panel1上设置一个参数来保存其图纸吗？

由于