【C#工具类】C#生成加减法验证码

来源：互联网发布：java 调用构造方法编辑：程序博客网时间：2024/06/05 00:48

开发出去的页面经常被别人以抓取的方式访问，造成服务器压力过大，IIS崩溃。这时候可以在经常被抓取的连接上添加验证码认证，可以有效的减轻服务器压力。
1.验证码输入页面
js：

function ValidateInput() {           var Num = document.getElementById("txtNum").value;            if (Num == "" || Num == str) {                alert("请输入验证码！");                return false;            }                     return true;        }

页面：

  <img src="ValidCode.aspx" alt="验证码"/> <asp:TextBox ID="txtNum" runat="server" Width="40px"></asp:TextBox>                        <asp:Button ID="btnContinue" runat="server" Text="查询" ToolTip="查询信息" OnClick="btnContinue_Click"                            OnClientClick="return ValidateInput();" />

这里IMG是一个页面生成的，这个页面也是重点。最后说，现在看验证。
2.后台验证

 protected void btnContinue_Click(object sender, EventArgs e)        {            try            {                if (txtNum.Text == Session["ValidCode"].ToString())                {          //.....Other Operation                 }                else                 {                    RaiseAlert("验证码错误！");                }                txtNum.Text = "";            }            catch (Exception ex)            {                lblMsg.Text = ex.Message;            }

3.验证码生成：
1）.页面：（就是一个正常的页面。）

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="ValidCode.aspx.cs" Inherits="Admin_ValidCode" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" ><head runat="server">    <title>无标题页</title></head><body>    <form id="form1" runat="server">    <div>    </div>    </form></body></html>

2）后台生成：

using System;using System.Data;using System.Configuration;using System.Collections;using System.Web;using System.Web.Security;using System.Web.UI;using System.Web.UI.WebControls;using System.Web.UI.WebControls.WebParts;using System.Web.UI.HtmlControls;using System.Drawing;//from http://i.aspx1.compublic partial class Admin_ValidCode : System.Web.UI.Page{    protected void Page_Load(object sender, EventArgs e)    {        this.CreateCheckCodeImage(GenerateCheckCode());    }    private string GenerateCheckCode()    {        int intFirst, intSec, intTemp;        string checkCode = String.Empty;        System.Random random = new Random();        intFirst = random.Next(1, 10);        intSec = random.Next(1, 10);        switch (random.Next(1, 3).ToString())        {            case "2":                if (intFirst < intSec)                {                    intTemp = intFirst;                    intFirst = intSec;                    intSec = intTemp;                }                checkCode = intFirst + "-" + intSec + "=";                Session["ValidCode"] = intFirst - intSec;                break;            default:                checkCode = intFirst + "+" + intSec + "=";                Session["ValidCode"] = intFirst + intSec;                break;        }        //Response.Cookies.Add(new HttpCookie("ValidCode",Movie.Common.AES.EncryptAes(checkCode)));        return checkCode;    }    #region 产生波形滤镜效果    private const double PI = 3.1415926535897932384626433832795;    private const double PI2 = 6.283185307179586476925286766559;    private System.Drawing.Bitmap TwistImage(Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase)    {        System.Drawing.Bitmap destBmp = new Bitmap(srcBmp.Width, srcBmp.Height);        // 将位图背景填充为白色        System.Drawing.Graphics graph = System.Drawing.Graphics.FromImage(destBmp);        graph.FillRectangle(new SolidBrush(System.Drawing.Color.White), 0, 0, destBmp.Width, destBmp.Height);        graph.Dispose();        double dBaseAxisLen = bXDir ? (double)destBmp.Height : (double)destBmp.Width;        for (int i = 0; i < destBmp.Width; i++)        {            for (int j = 0; j < destBmp.Height; j++)            {                double dx = 0;                dx = bXDir ? (PI2 * (double)j) / dBaseAxisLen : (PI2 * (double)i) / dBaseAxisLen;                dx += dPhase;                double dy = Math.Sin(dx);                // 取得当前点的颜色                int nOldX = 0, nOldY = 0;                nOldX = bXDir ? i + (int)(dy * dMultValue) : i;                nOldY = bXDir ? j : j + (int)(dy * dMultValue);                System.Drawing.Color color = srcBmp.GetPixel(i, j);                if (nOldX >= 0 && nOldX < destBmp.Width                 && nOldY >= 0 && nOldY < destBmp.Height)                {                    destBmp.SetPixel(nOldX, nOldY, color);                }            }        }        return destBmp;    }    #endregion    private void CreateCheckCodeImage(string checkCode)    {        if (checkCode == null || checkCode.Trim() == String.Empty)            return;        System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 15.0)), 25);        Graphics g = Graphics.FromImage(image);        try        {            //生成随机生成器            Random random = new Random();            //清空图片背景色            g.Clear(Color.White);            //画图片的背景噪音线            for (int i = 0; i < 12; i++)            {                int x1 = random.Next(image.Width);                int x2 = random.Next(image.Width);                int y1 = random.Next(image.Height);                int y2 = random.Next(image.Height);                g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);            }            Font font = new System.Drawing.Font("Arial", 16, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));            System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);            g.DrawString(checkCode, font, brush, 1, 1);            //画图片的前景噪音点            //for (int i = 0; i < 100; i++)            //{            //    int x = random.Next(image.Width);            //    int y = random.Next(image.Height);            //    image.SetPixel(x, y, Color.FromArgb(random.Next()));            //}            //image = TwistImage(image, true, 3, 1);//画图片的波形滤镜效果            //画图片的边框线            g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);            System.IO.MemoryStream ms = new System.IO.MemoryStream();            image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);            Response.ClearContent();            Response.ContentType = "image/Gif";            Response.BinaryWrite(ms.ToArray());        }        finally        {            g.Dispose();            image.Dispose();        }    }}

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