自已写的帮儿子出口算题的程序

儿子开学要上二年级了,每天数学做业的都要家长出一些口算题.今天写了一个程序可以出题并打印.自已对.net打印这部分不是很熟．现在只能打印单页．请哪位高手帮我改一下能打印多页．

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.IO;

namespace WindowsApplication1
{
    public partial class Form1 : Form
    {
        private Font printFont;
        private Random x;
        public Form1()
        {
            InitializeComponent();
        }
        public string getString()
        {
            
            x = new Random();
            int a, b,c,d,e,f;
   
            string g = string.Empty;
            string s = string.Empty;
            for (int i = 0; i < 30; i++)
            {
                a = x.Next(5, 100);
                b = x.Next(5, 100);
                c = x.Next(5, 100);
                d = x.Next(5, 100);
                e = x.Next(5, 100);
                f = x.Next(5, 100);
              
                if (a > b)
                {
                    g = a.ToString().PadRight(2) + " - " + b.ToString().PadRight(2) + " = " + "\t";
                }
                else
                {
                    g = a.ToString().PadRight(2) + " + " + b.ToString().PadRight(2) + " = " + "\t";
                }
                if (c > d)
                {
                    g += c.ToString().PadRight(2) + " - " + d.ToString().PadRight(2) + " = " + "\t";
                }
                else
                {
                    g += c.ToString().PadRight(2) + " + " + d.ToString().PadRight(2) + " = " + "\t";
                }
                if (e > f)
                {
                    g += e.ToString().PadRight(2) + " - " + f.ToString().PadRight(2) + " = " + "\t";
                }
                else
                {
                    g += e.ToString().PadRight(2) + " + " + f.ToString().PadRight(2) + " = " + "\t";
                }
               
                s += g + "\r\n";
            }
            return s;
        }
       
        private void button1_Click(object sender, EventArgs e)
        {
            textBox1.Text = null;
            textBox1.Text = getString();
          
        }

        private void button2_Click(object sender, EventArgs e)
        {
            printFont = new Font("宋体", 20,FontStyle.Bold);
            printDocument1 = new System.Drawing.Printing.PrintDocument();
            printDocument1.PrintPage += new System.Drawing.Printing.PrintPageEventHandler(printDocument1_PrintPage);
            if (printDialog1.ShowDialog() == DialogResult.OK)
            {
                printDocument1.Print();
            }
        }

        void printDocument1_PrintPage(object sender, System.Drawing.Printing.PrintPageEventArgs ev)
        {
            float linesPerPage = 0;
            float yPos = 0;
            float leftMargin = ev.MarginBounds.Left;
            float topMargin = ev.MarginBounds.Top;
            int count = 0;
            // Calculate the number of lines per page.
            linesPerPage = ev.MarginBounds.Height /
               printFont.GetHeight(ev.Graphics);

            // Print each line of the file.
            char[] c =  { '\n' };
            string[] a = textBox1.Text.Split(c);
            foreach(string s in a)
            {
                yPos = topMargin + (count *
                   printFont.GetHeight(ev.Graphics));
                ev.Graphics.DrawString(s + "\r\n", printFont, Brushes.Black,
                   leftMargin, yPos);
                count++;
            }
           ev.HasMorePages = false; 
        }
    }
}