C#编写的简单的验证码

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

namespace WindowsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            drawBmp(lbl1, 4);
        }

        private void Form1_Click(object sender, EventArgs e)
        {
            drawBmp(lbl1,4);
        }
        //生成所有用到的字符和数字集合 得到字符串 str
        public string GetAllStr() {
            string str = "";
            for (int i = 0; i < 10; i++) {
                str += i;
            }
            for (int i = (int)'a'; i <= (int)'z'; i++)
            {
                str += (char)i;
            }
            for (int i = (int)'A'; i <= (int)'Z'; i++) {
                str += (char)i;
            }
            return str;
        }
        //生成随机字符串 ，参数len 控制验证码长度
        public string GetRndStr(int len) {
            string str2 = "";
            string str = GetAllStr();
            char[] rndChar = str.ToCharArray();
            Random rnd = new Random();
            for (int i = 0; i < len; i++) {
                int k = rnd.Next(str.Length);
                str2+=rndChar[k];
            }
            return str2;
        }

        public Font set_font( int numFs) {
            Font font = null;
            switch (numFs) {
                case 0: font = new Font("宋体",16,FontStyle.Bold); break;
                case 1: font = new Font("宋体", 16, FontStyle.Italic); break;
                case 2: font = new Font("宋体", 16,FontStyle.Regular); break;
                default: font = new Font("宋体", 16,FontStyle.Strikeout); break;
            }
             return Font;
        }

        /*
         * 参数lbl是控件Label的名字,Label控件可改为其他控件，如PictureBox等
         * 参数rndNumLen
         */
        public void drawBmp(Label lbl, int rndNumLen)
        {
            Random r = new Random();
            string rndStr = GetRndStr(rndNumLen);
            Bitmap bmp = new Bitmap(80, 40);
            Graphics g = Graphics.FromImage(bmp);
            g.Clear(Color.LightBlue);
            g.DrawRectangle(new Pen(Color.Black), 0, 0, 80,40);
            Font f = new Font("宋体",16,FontStyle.Bold|~FontStyle.Strikeout&~FontStyle.Underline);
            SolidBrush sBrush = new SolidBrush(Color.Red);
            StringFormat strFormat=new StringFormat();
            strFormat.FormatFlags = StringFormatFlags.NoClip;
            char[] rndChar = rndStr.ToCharArray();
            for (int i = 0; i < rndNumLen; i++) {
                g.DrawString(rndChar[i].ToString(), f, sBrush, 1+20*i, 0, strFormat);
            }
               

            /**
             * 生成背景上的点 100个
             */
           
            Pen p = new Pen(Color.Green, 10);
            for (int i = 0; i < 10; i++) {
                for (int j = 0; j < 10; j++) {
                    int x = r.Next(bmp.Width);
                    int y = r.Next(bmp.Height);
                    bmp.SetPixel(x,y,Color.Green);
                }
            }
            /**
             * 生成背景的线条 2×rndNumLen个
             */
            for (int i = 0; i < 2*rndNumLen; i++) {
                int x1 = r.Next(bmp.Width);
                int y1 = r.Next(bmp.Height);
                int x2 = r.Next(bmp.Width);
                int y2 = r.Next(bmp.Height);
                g.DrawLine(new Pen(Color.Gray), new Point(x1,y1), new Point(x2,y2));
            }
            /**
             * 把图片负载在空间上
             */
                lbl.Image = bmp;
        }

    }
}