登录页面的验证码的生成

不难发现每次在我们登录注册一个网站时都会有相应的验证码出现来验证，其实实现漂亮的验证码也不难，下面我们就一起来实现漂亮的验证码

一般验证码的生成方法都是相同的,主要的步骤都有两步

第一步是：随机出一系统验证码的数字或字母，顺便把随机生成的数字或字母写入Cookies 或者 Session.

第二步是：用第一步随机出来的数字或字母来合成图片。

可以看出来验证码的复杂度主要是第二步来完成，你可以根据自己所要的复杂度来设定

好，基本原理知道了

我们一起来看看

 第一步：随机生成数字或字母的方法

/// <summary>
    /// 生成验证码的随机数
    /// </summary>
    /// <returns>返回五位随机数</returns>
    private string GenerateCheckCode()
    {
        int number;
        char code;
        string checkCode = String.Empty;

        Random random = new Random();

        for (int i = 0; i < 5; i++)//可以任意设定生成验证码的位数
        {
            number = random.Next();

            if (number % 2 == 0)
                code = (char)('0' + (char)(number % 10));
            else
                code = (char)('A' + (char)(number % 26));

            checkCode += code.ToString();
        }

        Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));//写入COOKIS
        Session["CheckCode"] = checkCode;  //写入Session，可以任意选一下
        return checkCode;
    }
第二步：生成图片

 /// <summary>
    /// 生成验证码图片
    /// </summary>
    /// <param name="checkCode"></param>
    private void CreateCheckCodeImage(string checkCode)
    {
        if (checkCode == null || checkCode.Trim() == String.Empty)
            return;

        Bitmap image = new Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 22);
        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 < 25; 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", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
            LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
            g.DrawString(checkCode, font, brush, 2, 2);

            //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()));
            }

            //画图片的边框线
            g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);

            MemoryStream ms = new MemoryStream();
            image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
            Response.ClearContent();
            Response.ContentType = "image/Gif";
            Response.BinaryWrite(ms.ToArray());
        }
        finally
        {//释放对象资源
            g.Dispose();
            image.Dispose();
        }
完整程序

先在VS2005里面的项目里面添加一个 checkCode.aspx 文件，在checkCode.aspx.cs 代码文件中添加如下完整代码

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;
using System.IO;
using System.Drawing.Drawing2D;

public partial class checkCode : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        CreateCheckCodeImage(GenerateCheckCode());//调用下面两个方法;
    }

    /// <summary>
    /// 生成验证码的随机数
    /// </summary>
    /// <returns>返回五位随机数</returns>
    private string GenerateCheckCode()
    {
        int number;
        char code;
        string checkCode = String.Empty;

        Random random = new Random();

        for (int i = 0; i < 5; i++)//可以任意设定生成验证码的位数
        {
            number = random.Next();

            if (number % 2 == 0)
                code = (char)('0' + (char)(number % 10));
            else
                code = (char)('A' + (char)(number % 26));

            checkCode += code.ToString();
        }

        Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));//写入COOKIS
        Session["CheckCode"] = checkCode;  //写入Session，可以任意选一下
        return checkCode;
    }

    /// <summary>
    /// 生成验证码图片
    /// </summary>
    /// <param name="checkCode"></param>
    private void CreateCheckCodeImage(string checkCode)
    {
        if (checkCode == null || checkCode.Trim() == String.Empty)
            return;

        Bitmap image = new Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 22);
        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 < 25; 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", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
            LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
            g.DrawString(checkCode, font, brush, 2, 2);

            //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()));
            }

            //画图片的边框线
            g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);

            MemoryStream ms = new MemoryStream();
            image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
            Response.ClearContent();
            Response.ContentType = "image/Gif";
            Response.BinaryWrite(ms.ToArray());
        }
        finally
        {//释放对象资源
            g.Dispose();
            image.Dispose();
        }
    }

}

上面生成验证码的页面都做好了，我们来调用看看

在你需要用到验证码的地方加了Image控件

<asp:Image ID="Image1" runat="server" ImageUrl="~/checkCode.aspx" />
这样验证码就会显示到Image控件上面了！

显示弄好了，当然我们要判断一下用户的输入是否正确！

只要我们取得用户输入的值跟Cookis或者Session对比就OK了

取Cookies的值 Request.Cookies["CheckCode"].Value

取Session的值 Session["CheckCode"].ToString() （最好先判断Session是否空）

如果不要区分大小写的话，就把用户输入的值和Cookies或Session的值都转成大写或都小写

 附用法     protected void Button1_Click(object sender, EventArgs e)
    {
        if (Request.Cookies["CheckCode"].Value == TextBox1.Text.Trim().ToString())
        {
            Response.Write("Cookies is right");
        }
        else
        {
            Response.Write("Cookies is wrong");
        }

        if (Session["CheckCode"] != null)
        {
            if (Session["CheckCode"].ToString().ToUpper() == TextBox1.Text.Trim().ToString().ToUpper())
                //这样写可以不能区分大小写
            {
                Response.Write("Session is right");

            }
            else
            {
                Response.Write("Session is wrong");
            }
        }
    }