验证码

新建vcode.aspx页面

vcode.aspx.cs代码为

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

public partial class admin_vcode : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        this.ValidateCode(RndNum(4));
    }

    /// <summary>
    /// 该方法是将生成的随机数写入图像文件
    /// </summary>
    /// <param name="VNum">VNum是一个随机数</param>
    private void ValidateCode(string VNum)
    {
        Bitmap Img = null;
        Graphics g = null;
        MemoryStream ms = null;

        int gheight = VNum.Length * 12;//定义图像的大小
        Img = new Bitmap(gheight, 25);//生成图像的实例
        g = Graphics.FromImage(Img);//从Img对象生成新的Graphics对象
        Font f = new Font("Arial Black", 10);//生成Font类的实例
        SolidBrush s = new SolidBrush(Color.White);//生成笔刷类的实例
        g.DrawString(VNum, f, s, 3, 3);//将VNum写入图片中
        ms = new MemoryStream();//生成内存流对象
        Img.Save(ms, ImageFormat.Jpeg);//将此图像以Png图像文件的格式保存到流中
        Response.ClearContent();//更改http ContentType
        Response.ContentType = "image/Jpeg";
        Response.BinaryWrite(ms.ToArray());//将整个二进制流的内容写入字节数组
        //回收资源
        g.Dispose();
        Img.Dispose();
        Response.End();

    }
    /// <summary>
    /// 该方法用于生成指定位数的随机数
    /// </summary>
    /// <param name="VcodeNum">参数是随机数的位数</param>
    /// <returns>返回一个随机数字符串</returns>
    private string RndNum(int VcodeNum)
    {
        string Vchar = "0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p" +
            ",q,r,s,t,u,v,w,x,y,z,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q" +
            ",R,S,T,U,V,W,X,Y,Z";
        string[] VcArray = Vchar.Split(new Char[] { ',' });//拆分成数组
        string VNum = "";
        int temp = -1;//记录上次随机数值，尽量避避免生产几个一样的随机数

        Random rand = new Random();
        //采用一个简单的算法以保证生成随机数的不同
        for (int i = 1; i < VcodeNum + 1; i++)
        {
            if (temp != -1)
            {
                rand = new Random(i * temp * unchecked((int)DateTime.Now.Ticks));
            }

            int t = rand.Next(61);
            if (temp != -1 && temp == t)
            {
                return RndNum(VcodeNum);

            }
            temp = t;
            VNum += VcArray[t];
        }
        Session["code"] = VNum;
        return VNum;
    }
}

 

在需要用到验证码的引用页面：<asp:Image ID="Image1" runat="server" ImageUrl="vcode.aspx" />或者
                <img src="vcode.aspx" alt="看不清楚，重新一张" onclick="this.src='vcode.aspx?abc='+Math.random()" style="cursor:pointer;" />

后台用session（"名称") 即session("code")去匹配TextBox的输入。