asp.net随机数字验证码

       今天下午写了一个关于验证码的代码，是用的一个生成随机数字的一个验证码。如果你有所需要，程序COPY就可以使用了，有很好的注释，很适合初学者。下面我就给出我的代码吧.

showcode.aspx:

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="showcode.aspx.cs" Inherits="Ajax_Login_showcode" %>

主要代码页面：
showcode.aspx.cs:

using System;
using System.Text;
using System.Drawing;
using System.Drawing.Imaging;
using System.Drawing.Drawing2D;
using System.IO;

public partial class Ajax_Login_showcode : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!this.IsPostBack)
        {
            this.CreateValidateImage(4);
        }
    }
    /// <summary>
    /// ValidateCode 的摘要说明
    /// </summary>
        private const double ImageLengthBase = 12.5;
        private const int ImageHeight = 22;
        private const int ImageLinenumber = 25;
        private const int ImagePointnumber = 100;
        public static string VALIDATECODEKEY = "VALIDATECODEKEY";
        private int length = 4;
        private string code = string.Empty;
        /// <summary>
        /// 获取或设置验证码长度，默认值为4
        /// </summary>
        public int Length
        {
            get
            {
                return length;
            }
            set
            {
                length = value;
            }
        }
        /// <summary>
        /// 获取验证码
        /// </summary>
        public string Code
        {
            get
            {
                return code;
            }
        }
        /// <summary>
        /// 创建随机验证码
        /// </summary>
        public string CreateCode(int length)
        {
            if (length <= 0)
            {
                return string.Empty;
            }
            //创建一组随机数，并构成验证码
            Random random = new Random();
            StringBuilder sbCode = new StringBuilder();
            for (int i = 0; i < length; i++)
            {
                sbCode.Append(random.Next(0, 10));
            }
            //保存验证码到Session对象中
            code = sbCode.ToString();
            Session[VALIDATECODEKEY] = code;
            return code;
        }
        /// <summary>
        /// 创建验证码的图片和验证码
        /// </summary>
        public void CreateValidateImage(string code)
        {
            if (string.IsNullOrEmpty(code) == true) return;
            //保存验证码到Session对象中
            Session[VALIDATECODEKEY] = code;
            //创建一个图像
            Bitmap image = new Bitmap((int)Math.Ceiling((code.Length * ImageLengthBase)), ImageHeight);
            Graphics g = Graphics.FromImage(image);

            //随机数生成器
            Random random = new Random();
            try
            {    //清空图像，并指定填充颜色
                g.Clear(Color.White);
                //绘制图片干扰线
                int x1, x2, y1, y2;
                for (int i = 0; i < ImageLinenumber; i++)
                {
                    x1 = random.Next(image.Width);
                    y1 = random.Next(image.Height);
                    x2 = random.Next(image.Width);
                    y2 = random.Next(image.Height);
                    //绘制干扰线
                    g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
                }
                //绘制验证码
                Font font = new Font("Tahoma", 12, FontStyle.Bold | FontStyle.Italic);
                LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkBlue, 1.2f, true);
                g.DrawString(code, font, brush, 2.0f, 2.0f);
                //画图片的前景噪音点
                int x, y;
                for (int i = 0; i < ImagePointnumber; i++)
                {
                    x = random.Next(image.Width);
                    y = random.Next(image.Height);
                    //绘制点
                    image.SetPixel(x, y, Color.FromArgb(random.Next()));
                }
                //绘制图片的边框线
                g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
                //保存图片中的内容到流中
                MemoryStream ms = new MemoryStream();
                image.Save(ms, ImageFormat.Gif);
                //输出图片
                Response.ClearContent();
                Response.ContentType = "image/Gif";
                Response.BinaryWrite(ms.ToArray());
            }
            finally
            {   //释放占有的资源
                g.Dispose();
                image.Dispose();
            }
        }
        /// <summary>
        /// 创建验证码的图片和验证码
        /// </summary>
        public void CreateValidateImage(int length)
        {   //创建验证码
            code = CreateCode(length);
            //创建验证码图片
            CreateValidateImage(code);
        }
}
显示页面：

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default2.aspx.cs" Inherits="Ajax_Login_Default2" %>
<head runat="server">
    <title>无标题页</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:Image ID="Image1" runat="server" ImageUrl ="~/Ajax_Login/showcode.aspx" />
        <br />
    </form>
</body>
</html>
很好的验证码，很使用，希望对大家有所帮助。