asp.net 验证码

CreateVCI .aspx.cs：

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Drawing;//基本绘图
using System.Drawing.Drawing2D;//支持2D和矢量绘图，可消除锯齿、几何转换和图形路径
using System.IO;//流，用于输出图片
using System.Drawing.Imaging;//处理图像

public partial class CreateVCI : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            //生成5位随机数验证码
            CreatePic(RandomNum(5));
        }
    }
    /// <summary>
    /// 生成随机数
    /// </summary>
    /// <param name="Len">控制生成随机数的位数</param>
    /// <returns></returns>
    public string RandomNum(int Len)
    {
        string str = "0,1,2,3,4,5,6,7,8,9,";
        str += "a,b,c,d,e,f,g,h,i,j,k,m,n,p,q,r,s,t,u,v,w,x,y,z,";
        str += "A,B,C,D,E,F,G,H,J,K,L,M,N,P,Q,R,S,T,U,V,W,X,Y,Z"; 

        string[] s = str.Split(new char[] { ',' });//将字符串才分成字符串数组;
        string strNum = String.Empty;
        int tag = -1;//用于记录上一个随机数的值，避免产生2个重复值;
        Random rnd = new Random();
        //产生一个长为Len的随机字符串;
        for (int i = 1; i <= Len; i++)
        {
            if (tag == -1)
            {
                rnd = new Random(i * tag * unchecked((int)DateTime.Now.Ticks));//初始化一个随机数实例;
            }
            int rndNum = rnd.Next(0,57);//返回小于24个字符的非负随机数
            if (tag != -1 && tag == rndNum)
            {
                return RandomNum(Len);//返回该方法
            }
            tag = rndNum;
            strNum += s[rndNum];
        }
        //将生成的随机数保存在session中
        Session["CheckCode"] = strNum;
        return strNum;
    }
    /// <summary>
    /// 为图片添加干扰
    /// </summary>
    /// <param name="checkCode">绘制验证码</param>
    private void CreatePic(string checkCode)
    {
        if (checkCode == null || checkCode.Trim() == String.Empty)
        return;
        Bitmap image = new Bitmap(checkCode.Length * 20 + 10, 36);//定义图像
        Graphics g = Graphics.FromImage(image);//创建新的image绘图对象
        try
        {
            //随机生成器
            Random random = new Random();
            //清空图片背景颜色;
            g.Clear(Color.AliceBlue);
            //画图片的背景噪音线
            for (int i = 0; i < 50; 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);
                //获取系统的颜色画曲线
                g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
            }
            //画图片字体和字号
            Font font = new Font("Arial", 20, (FontStyle.Bold | FontStyle.Italic | FontStyle.Strikeout));
            //初始画刷
            LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.BlueViolet, Color.Crimson, 12f, true);
            g.DrawString(checkCode, font, brush, 2, 3);//绘制指定文本的字符串
            //图片前的噪音点
            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()));//获取指定的颜色
            }
            //画图片的边框线
            g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
            //输出图像
            MemoryStream ms = new MemoryStream();
            image.Save(ms, ImageFormat.Gif);//将图片保存到指定流
            Response.ClearContent();//清楚缓冲区的流
            Response.ContentType = "imge.Gif";//配置输出类型
            Response.BinaryWrite(ms.ToArray());//输出内容
        }
        finally
        {
            //清空不需要的资源
            g.Dispose();
            image.Dispose();
        }
    }
}

print.aspx:

<script type="text/javascript">
function show(im)
{
    im.src="CreateVCI.aspx?"+new Date;
}
</script>
<img alt="点击图片刷新" src="CreateVCI.aspx" onclick="show(this)" />
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<asp:Button ID="Button1" runat="server" Text="Button" onclick="Button1_Click" />

 
print.aspx.cs:
    protected void Button1_Click(object sender, EventArgs e)
    {
        if (TextBox1.Text == Page.Session["CheckCode"].ToString())
        {
            Response.Write("<script> alert('验证码正确!');</script>");
        }
        else
        {
            Response.Write("<script> alert('验证码不正确!');</script>");
        }
    }

 

 

    不想多说，注释非常详细了。经VS2008编写，运行成功。