Asp.Net 动态生成验证码
用到验证码，可以有效地防止黑客软件的恶意破解
使用方法：
1、在Web项目中添加一个类，如“CreateImage.cs”，然后将我公布的源代码Copy进去；
2、再新建一个Web窗体，如“Image.aspx”，在Page_Load中加入代码 “CreateImage.DrawImage ();”当然别忘了加上对类的引用哦！！
3、在页面的合适位置上（你想放验证码的位置）上加上如下javascript代码就OK 了，
<SCRIPT LANGUAGE="javascript">
<!__
var numkey = Math.random();
numkey = Math.round(numkey*10000);
document.write("<img src=\"Image.aspx?k="+ numkey +"\" width=\"52\" height=\"23\" hspace=\"4\"");
//__>
</SCRIPT>
源代码如下：
/// <summary>
/// 验证码模块
/// </summary>
public class CreateImage
{
public static void DrawImage()
{
CreateImage img=new CreateImage();
HttpContext.Current.Session["CheckCode"]=img.RndNum(4);
img.CreateImages(HttpContext.Current.Session["CheckCode"].ToString());
}
/// <summary>
/// 生成验证图片
/// </summary>
/// <param name="checkCode">验证字符</param>
private void CreateImages(string checkCode)
{
int iwidth = (int)(checkCode.Length * 13);
System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 23);
Graphics g = Graphics.FromImage(image);
g.Clear(Color.White);
//定义颜色
Color[] c = {Color.Black,Color.Red,Color.DarkBlue,Color.Green,Color.Orange,Color.Brown,Color.DarkCyan,Color.Purple};
//定义字体
string[] font = {"Verdana","Microsoft Sans Serif","Comic Sans MS","Arial","宋体"};
Random rand = new Random();
//随机输出噪点
for(int i=0;i<50;i++)
{
int x = rand.Next(image.Width);
int y = rand.Next(image.Height);
g.DrawRectangle(new Pen(Color.LightGray, 0),x,y,1,1);
}
//输出不同字体和颜色的验证码字符
for(int i=0;i<checkCode.Length;i++)
{
int cindex = rand.Next(7);
int findex = rand.Next(5);
Font f = new System.Drawing.Font(font[findex], 10, System.Drawing.FontStyle.Bold);
Brush b = new System.Drawing.SolidBrush(c[cindex]);
int ii=4;
if((i+1)%2==0)
{
ii=2;
}
g.DrawString(checkCode.Substring(i,1), f, b, 3+(i*12), ii);
}
//画一个边框
g.DrawRectangle(new Pen(Color.Black,0),0,0,image.Width-1,image.Height-1);
//输出到浏览器
System.IO.MemoryStream ms = new System.IO.MemoryStream();
image.Save(ms,System.Drawing.Imaging.ImageFormat.Jpeg);
HttpContext.Current.Response.ClearContent();
//Response.ClearContent();
HttpContext.Current.Response.ContentType = "image/Jpeg";
HttpContext.Current.Response.BinaryWrite(ms.ToArray());
g.Dispose();
image.Dispose();
}
/// <summary>
/// 生成随机的字母
/// </summary>
/// <param name="VcodeNum">生成字母的个数</param>
/// <returns>string</returns>
private string RndNum(int VcodeNum)
{
string Vchar = "0,1,2,3,4,5,6,7,8,9" ;
string[] VcArray = Vchar.Split(',') ;
string VNum = "" ; //由于字符串很短，就不用StringBuilder了
int temp = -1 ; //记录上次随机数值，尽量避免生产几个一样的随机数
//采用一个简单的算法以保证生成随机数的不同
Random rand =new Random();
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(VcArray.Length ) ;
if (temp != -1 && temp == t)
{
return RndNum( VcodeNum );
}
temp = t ;
VNum += VcArray[t];
}
return VNum ;
}
}
==============================================================
using System;
using System.IO;
using System.Drawing;
using System.Drawing.Imaging;
using System.Text;
using System.Collections;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class yzm : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
string chkCode = string.Empty;
//颜色列表，用于验证码、噪线、噪点
Color[] color = { Color.Black, Color.Red, Color.Blue, Color.Green, Color.Orange, Color.Brown, Color.Brown, Color.DarkBlue };
//字体列表，用于验证码
string[] font = { "Times New Roman", "MS Mincho", "Book Antiqua", "Gungsuh", "PMingLiU", "Impact" };
//验证码的字符集，去掉了一些容易混淆的字符
char[] character = { '2', '3', '4', '5', '6', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'J', 'K', 'L', 'M', 'N', 'P', 'R',
'S', 'T', 'W', 'X', 'Y' };
Random rnd = new Random();
//生成验证码字符串
for (int i = 0; i < 4; i++)
{
chkCode += character[rnd.Next(character.Length)];
}
Bitmap bmp = new Bitmap(80, 25);
Graphics g = Graphics.FromImage(bmp);
g.Clear(Color.White);
Session["yz"] = chkCode;//定义session值
//Session.Timeout = 1;
//画噪线
for (int i = 0; i < 5; i++)
{
int x1 = rnd.Next(80);
int y1 = rnd.Next(25);
int x2 = rnd.Next(80);
int y2 = rnd.Next(25);
Color clr = color[rnd.Next(color.Length)];
g.DrawLine(new Pen(clr), x1, y1, x2, y2);
}
//画验证码字符串
for (int i = 0; i < chkCode.Length; i++)
{
string fnt = font[rnd.Next(font.Length)];
Font ft = new Font(fnt, 17);
Color clr = color[rnd.Next(color.Length)];
g.DrawString(chkCode[i].ToString(), ft, new SolidBrush(clr), (float)i * 17 + 5, (float)0);
}
//画噪点
for (int i = 0; i < 80; i++)
{
int x = rnd.Next(bmp.Width);
int y = rnd.Next(bmp.Height);
Color clr = color[rnd.Next(color.Length)];
bmp.SetPixel(x, y, clr);
}
//清除该页输出缓存，设置该页无缓存
Response.Buffer = true;
Response.ExpiresAbsolute = System.DateTime.Now.AddMilliseconds(0);
Response.Expires = 0;
Response.CacheControl = "no-cache";
Response.AppendHeader("Pragma", "No-Cache");
//将验证码图片写入内存流，并将其以 "image/Png" 格式输出
MemoryStream ms = new MemoryStream();
try
{
bmp.Save(ms, ImageFormat.Png);
Response.ClearContent();
Response.ContentType = "image/Png";
Response.BinaryWrite(ms.ToArray());
}
finally
{
//显式释放资源
bmp.Dispose();
g.Dispose();
}
}
}
----------------------------
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="yzm.aspx.cs" Inherits="yzm" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>验证码</title>
</head>
<body>
<form id="form1" runat="server">
<div>
</div>
</form>
</body>
</html>
调用界面的JAVASCRIPT 设置点击图片自动换
<script type="text/javascript" language="javascript">
function yanzheng()
{
document.getElementById("<%= img1.ClientID%>").src="yzm.aspx";
}
</script>
<asp:Image ID="img1" runat="server" ImageUrl="~/yzm.aspx" onclick="yanzheng();" alt="点击刷新!" Height="25px" Width="80px" />
------------------------------------------------
后台页面 利用简单的SESSION判断
if(TextBox3.Text.ToUpper()!=Session["yz"].ToString())
{
Page.ClientScript.RegisterStartupScript(this.GetType(), "fdf", "<script>alert('验证码错误!');</script>");
}
