C-Sharp双缓冲绘制图形无闪烁

如何利用C#双缓冲绘制图形达到无闪烁的性能呢？

以下代码摘录自《stack over flow》https://stackoverflow.com/questions/2608909/c-sharp-graphics-flickering，提供了一种使用双缓冲的方式在Windows Form上进行绘制图形的方法，实测有效。

注意两点：

1. Windows Form的属性设置成DoubleBuffered = true
2. 注意Pen、Brushes等GDI的资源需要手动dispose

public partial class Form1 : Form
{
    int xFirst, yFirst;
    Bitmap bm = new Bitmap(1000, 1000);
    Graphics bmG;
    Pen pen = new Pen(Color.Black, 1);
    bool draw = false;

    public Form1()
    {
        InitializeComponent();
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        bmG = Graphics.FromImage(bm);
        bmG.Clear(Color.White);
    }

    private void Form1_MouseDown(object sender, MouseEventArgs e)
    {
        xFirst = e.X;
        yFirst = e.Y;
        draw = true;
    }

    private void Form1_MouseUp(object sender, MouseEventArgs e)
    {
        bmG.DrawLine(pen, xFirst, yFirst, e.X, e.Y);
        draw = false;
        Invalidate();
    }

    private void Form1_MouseMove(object sender, MouseEventArgs e)
    {
        if (draw)
        {
            Invalidate();
        }
    }

    private void Form1_Paint(object sender, PaintEventArgs e)
    {
        if (draw) {
            e.Graphics.DrawImage(bm, 0, 0);
            e.Graphics.DrawLine(pen, xFirst, yFirst, e.X, e.Y);
        } else {
            e.Graphics.DrawImage(bm, 0, 0);
        }
    }
}