实现效果如下：（随机生成）

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Windows.Forms;

namespace WindowsFormsApplication5

{

    public partial class Form1 : Form

{

    public Form1()

    {

        this.AutoScaleBaseSize = new Size(6, 14);

        this.ClientSize = new Size(600, 400);

        this.Paint += new PaintEventHandler(this.Form1_Paint);//注册paint事件

        this.Click+=new EventHandler(this.Redraw);//注册单击事件

    }

    private void Redraw(object sender, EventArgs e)

    {

        this.Invalidate();//使窗口重绘

    }

    private void Form1_Paint(object sender, PaintEventArgs e)

    {

        graphics = e.Graphics ;

        drawTree( 10, 200, 310, 100, -PI/2 );

    }

    private Graphics graphics;

    const double PI = Math.PI;

    double th1 = 40 * Math.PI / 180;

    double th2 = 30 * Math.PI / 180;

    double per1 = 0.6;

    double per2 = 0.7;

    Random rnd = new Random();

    double rand()

    {

        return rnd.NextDouble();

    }

    void drawTree(int n,

            double x0, double y0, double leng, double th)

    {

        if( n==0 ) return;

        double x1 = x0 + leng * Math.Cos(th);

        double y1 = y0 + leng * Math.Sin(th);

        drawLine(x0, y0, x1, y1, n/2);

        drawTree( n - 1, x1, y1, per1 * leng*(0.5+rand()), th + th1*(0.5+rand()) );//使用递归算法反复执行drawTree方法，直到n=0，跳出

        drawTree( n - 1, x1, y1, per2 * leng*(0.4+rand()), th - th2*(0.5+rand()) );

        if (rand() > 0.6)

            drawTree(n - 1, x1, y1, per2 * leng * (0.4 + rand()), th - th2 * (0.5 + rand()));

    }

    void drawLine( double x0, double y0, double x1, double y1, int width ){

        graphics.DrawLine(

            new Pen(Color.Blue, width ),

            (int)x0, (int)y0, (int)x1, (int)y1 );

    }

}

}