需要引入一个ashx的一般处理程序！
把这个程序在前台当作一个图片使用就可以！
前台代码：
<td>
<img title="看不清？" style=" cursor:pointer ;vertical-align:middle" width="45px" src="../ValidateCode.ashx" onclick="this.src='../ValidateCode.ashx?_='+Math.random()" />
</td>
cursor:pointer 光标呈现为指示链接的指针（一只手）
onclick 点击切换图片
Math.random()随机数，改变切换地址，有些浏览器点击的时候不自动切换，直接调用缓存文件（如IE）
验证码一般处理程序ashx:
不知道为什么传不上来啊附件，我就把代码贴上来吧，大家回去用这个代码建立一个ashx的文件就OK了
建议验证码存到【session】里面，下面的代码是存到session里的（使用其他方法的可以注释掉context.Session["code"] = code;）
//一般处理程序中使用session，必须实现一个接口
首先添加一个命名空间“using System.Web.SessionState;”
我把我的后台登录的判断处代码贴到下面，也许对大家的理解有帮助。。。。
<%@ WebHandler Language="C#" Class="ValidateCode" %> using System;
using System.Web;
using System.Drawing;
using System.Web.SessionState;
public class ValidateCode : IHttpHandler, IRequiresSessionState { public void ProcessRequest(HttpContext context)
{
context.Response.ContentType = "image/jpeg";
string code = GetRndStr();//生成4个随机的字符 //记录生成的验证码到session
context.Session["code"] = code; using (Bitmap img = CreateImages(code, "ch"))
{
img.Save(context.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
}
} public bool IsReusable
{
get
{
return false;
}
}
/// <summary>
/// 数字随机数
/// </summary>
/// <returns></returns>
private string GetRndNum()
{
string code = string.Empty;
Random random = new Random();
for (int i = ; i < ; i++)
{
code += random.Next();
}
return code;
}
/// <summary>
/// 英文随机
/// </summary>
/// <returns></returns>
private string GetRndStr()
{
string Vchar = "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(',');
string checkCode = string.Empty;
Random rand = new Random();
for (int i = ; i < ; i++)
{
int t = rand.Next(VcArray.Length);
checkCode += VcArray[t];
}
return checkCode;
}
/// <summary>
/// 中文随机
/// </summary>
/// <returns></returns>
private string GetRndCh()
{
System.Text.Encoding gb = System.Text.Encoding.Default;//获取GB2312编码页（表）
object[] bytes = CreateRegionCode();//生4个随机中文汉字编码
string[] str = new string[];
System.Text.StringBuilder sb = new System.Text.StringBuilder();
for (int i = ; i < ; i++)
{
//根据汉字编码的字节数组解码出中文汉字
str[i] = gb.GetString((byte[])Convert.ChangeType(bytes[i], typeof(byte[])));
sb.Append(str[i].ToString());
}
return sb.ToString();
}
/// <summary>
/// 产生随机中文字符
/// </summary>
/// <param name="strlength"></param>
/// <returns></returns>
private static object[] CreateRegionCode(int strlength)
{
//定义一个字符串数组储存汉字编码的组成元素
string[] rBase = new String[] { "", "", "", "", "", "", "", "", "", "", "a", "b", "c", "d", "e", "f" };
Random rnd = new Random();
object[] bytes = new object[strlength]; for (int i = ; i < strlength; i++)
{
//区位码第1位
int r1 = rnd.Next(, );
string str_r1 = rBase[r1].Trim();
//区位码第2位
rnd = new Random(r1 * unchecked((int)DateTime.Now.Ticks) + i);
int r2;
if (r1 == )
{
r2 = rnd.Next(, );
}
else
{
r2 = rnd.Next(, );
}
string str_r2 = rBase[r2].Trim(); //区位码第3位
rnd = new Random(r2 * unchecked((int)DateTime.Now.Ticks) + i);//更换随机种子
int r3 = rnd.Next(, );
string str_r3 = rBase[r3].Trim(); //区位码第4位
rnd = new Random(r3 * unchecked((int)DateTime.Now.Ticks) + i);
int r4;
if (r3 == )
{
r4 = rnd.Next(, );
}
else if (r3 == )
{
r4 = rnd.Next(, );
}
else
{
r4 = rnd.Next(, );
}
string str_r4 = rBase[r4].Trim();
//定义两个字节变量存储产生的随机汉字区位码
byte byte1 = Convert.ToByte(str_r1 + str_r2, );
byte byte2 = Convert.ToByte(str_r3 + str_r4, ); //将两个字节变量存储在字节数组中
byte[] str_r = new byte[] { byte1, byte2 }; //将产生的一个汉字的字节数组放入object数组中
bytes.SetValue(str_r, i);
}
return bytes;
}
/// <summary>
/// 画图片的背景图+干扰线
/// </summary>
/// <param name="checkCode"></param>
/// <returns></returns>
private Bitmap CreateImages(string checkCode, string type)
{
int step = ;
if (type == "ch")
{
step = ;//中文字符，边界值做大
}
int iwidth = (int)(checkCode.Length * ( + step));
System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, );
Graphics g = Graphics.FromImage(image);
g.Clear(Color.White);//清除背景色
Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };//定义随机颜色
string[] font = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" };
Random rand = new Random(); for (int i = ; i < ; i++)
{
int x1 = rand.Next(image.Width);
int x2 = rand.Next(image.Width);
int y1 = rand.Next(image.Height);
int y2 = rand.Next(image.Height);
g.DrawLine(new Pen(Color.LightGray, ), x1, y1, x2, y2);//根据坐标画线
} for (int i = ; i < checkCode.Length; i++)
{
int cindex = rand.Next();
int findex = rand.Next(); Font f = new System.Drawing.Font(font[findex], , System.Drawing.FontStyle.Bold);
Brush b = new System.Drawing.SolidBrush(c[cindex]);
int ii = ;
if ((i + ) % == )
{
ii = ;
}
g.DrawString(checkCode.Substring(i, ), f, b, + (i * ( + step)), ii); }
g.DrawRectangle(new Pen(Color.Black, ), , , image.Width - , image.Height - );
System.IO.MemoryStream ms = new System.IO.MemoryStream();
return image;
}
}
判断session后天代码：
protected void btnLogin_Click(object sender, EventArgs e)
{ //学生 1 老师 2
string type = ddl.SelectedValue;
string no = txtNo.Text.Trim();
string pwd = txtPwd.Text.Trim();
//md5加密
pwd = Common.GetMd5(pwd); string code = txtCode.Text.Trim(); //验证码正确 因为session有过期失效的问题，
//ps:session在服务器上默认保存20分钟
if (Session["code"] != null && code.ToLower() == Session["code"].ToString().ToLower())
{
//
Session.Remove("code");
string msg;
//学生
if (type == "")
{ //判断用户名密码是否正确
ItcastOCSS.BLL.Student bll = new ItcastOCSS.BLL.Student();
ItcastOCSS.Model.Student stu = new ItcastOCSS.Model.Student();
if (bll.Login(no, pwd, out msg, out stu))
{
//记录登陆成功的状态
Session["user"] = stu;
//跳转
Response.Redirect("Student/Index.aspx");
}
lblMsg.Text = msg;
}
else if (type == "")
{
//老师
ItcastOCSS.BLL.Teacher bll = new ItcastOCSS.BLL.Teacher();
ItcastOCSS.Model.Teacher tea = new ItcastOCSS.Model.Teacher();
if (bll.Login(no, pwd, out msg, out tea))
{
Session["user"] = tea;
//跳转
if (tea.TIsAdmin == )
{
//管理员
Response.Redirect("Admin/Index.aspx");
}
else if(tea.TIsAdmin == )
{
//老师
Response.Redirect("Teacher/Index.aspx");
}
}
} }
else
{
//验证码错误
lblMsg.Text = "验证码错误";
} }
另外一个
using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Web; namespace CZBK.ItcastProject.Common
{
public class ValidateCode
{
public ValidateCode()
{
}
/// <summary>
/// 验证码的最大长度
/// </summary>
public int MaxLength
{
get { return ; }
}
/// <summary>
/// 验证码的最小长度
/// </summary>
public int MinLength
{
get { return ; }
}
/// <summary>
/// 生成验证码
/// </summary>
/// <param name="length">指定验证码的长度</param>
/// <returns></returns>
public string CreateValidateCode(int length)
{
int[] randMembers = new int[length];
int[] validateNums = new int[length];
string validateNumberStr = "";
//生成起始序列值
int seekSeek = unchecked((int)DateTime.Now.Ticks);
Random seekRand = new Random(seekSeek);
int beginSeek = (int)seekRand.Next(, Int32.MaxValue - length * );
int[] seeks = new int[length];
for (int i = ; i < length; i++)
{
beginSeek += ;
seeks[i] = beginSeek;
}
//生成随机数字
for (int i = ; i < length; i++)
{
Random rand = new Random(seeks[i]);
int pownum = * (int)Math.Pow(, length);
randMembers[i] = rand.Next(pownum, Int32.MaxValue);
}
//抽取随机数字
for (int i = ; i < length; i++)
{
string numStr = randMembers[i].ToString();
int numLength = numStr.Length;
Random rand = new Random();
int numPosition = rand.Next(, numLength - );
validateNums[i] = Int32.Parse(numStr.Substring(numPosition, ));
}
//生成验证码
for (int i = ; i < length; i++)
{
validateNumberStr += validateNums[i].ToString();
}
return validateNumberStr;
} /// <summary>
/// 创建验证码的图片
/// </summary>
/// <param name="containsPage">要输出到的page对象</param>
/// <param name="validateNum">验证码</param>
public void CreateValidateGraphic(string validateCode, HttpContext context)
{
Bitmap image = new Bitmap((int)Math.Ceiling(validateCode.Length * 12.0), );
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);
//画图片的干扰线
for (int i = ; i < ; 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 Font("Arial", , (FontStyle.Bold | FontStyle.Italic));
//渐变.
LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(, , image.Width, image.Height),
Color.Blue, Color.DarkRed, 1.2f, true);
g.DrawString(validateCode, font, brush, , ); //画图片的前景干扰点
for (int i = ; i < ; 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), , , image.Width - , image.Height - );
//保存图片数据
MemoryStream stream = new MemoryStream();
image.Save(stream, ImageFormat.Jpeg);
//输出图片流
context.Response.Clear();
context.Response.ContentType = "image/jpeg";
context.Response.BinaryWrite(stream.ToArray());
}
finally
{
g.Dispose();
image.Dispose();
}
}
/// <summary>
/// 得到验证码图片的长度
/// </summary>
/// <param name="validateNumLength">验证码的长度</param>
/// <returns></returns>
public static int GetImageWidth(int validateNumLength)
{
return (int)(validateNumLength * 12.0);
}
/// <summary>
/// 得到验证码的高度
/// </summary>
/// <returns></returns>
public static double GetImageHeight()
{
return 22.5;
}
}
}
本文转自：http://www.nbcoder.net/thread-337-1-1.html