C# 生成随机验证码的问题?
using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Text;using System.Windows.Forms;namespace RandomCode{ public partial class Form1 : Form { public Form1() { InitializeComponent(); } private Random rd; private int gg; protected override void OnPaint(PaintEventArgs e) { base.OnPaint(e); Graphics gh = e.Graphics; rd = new Random(); gg = rd.Next(1000, 10000); Font font = new Font(FontFamily.Families[5], 10); SolidBrush brush = new SolidBrush(Color.SandyBrown); gh.DrawString(gg.ToString(),font,brush, 0, 0); } private void Draw_Click(object sender, EventArgs e) { Rectangle rc = new Rectangle(0,0,40,20); this.Invalidate(rc); } private void Check_Click(object sender, EventArgs e) { try { if (gg != Convert.ToInt32(message.Text.Trim())) { MessageBox.Show("请输入正确的验证码"); } } catch (FormatException exp) { MessageBox.Show(exp.Message); } } }}