首先需要建立一个aspx文件或者ashx文件。后者最佳，不过本文采用aspx。
假设这个文件名为Img.aspx ,那么cs文件如下：
protectedvoid Page_Load(object sender, EventArgs e)
{
string[] str = new string[4];
string serverCode = "";
//生成随机生成器
Random random = new Random();
for (int i = 0; i < 4; i++)
{
str[i] = random.Next(10).ToString().Substring(0, 1);
}
CreateCheckCodeImage(str);
foreach (string s in str)
{
serverCode += s;
}
Session["serverCode"] = serverCode;
}
private void CreateCheckCodeImage(string[] checkCode)
{
if (checkCode == null || checkCode.Length <= 0)
return;
System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 32.5)), 30);
System.Drawing.Graphics g = Graphics.FromImage(image);
try
{
Random random = new Random();
//清空图片背景色
g.Clear(Color.White);
//画图片的背景噪音线
for (int i = 0; i < 20; 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);
}
//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[] f = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" };
for (int k = 0; k <= checkCode.Length - 1; k++)
{
int cindex = random.Next(7);
int findex = random.Next(5);
Font drawFont = new Font(f[findex], 16, (System.Drawing.FontStyle.Bold));
SolidBrush drawBrush = new SolidBrush(c[cindex]);
float x = 5.0F;
float y = 0.0F;
float width = 20.0F;
float height = 25.0F;
int sjx = random.Next(10);
int sjy = random.Next(image.Height - (int)height);
RectangleF drawRect = new RectangleF(x + sjx + (k * 25), y + sjy, width, height);
StringFormat drawFormat = new StringFormat();
drawFormat.Alignment = StringAlignment.Center;
g.DrawString(checkCode[k], drawFont, drawBrush, drawRect, drawFormat);
}
//画图片的前景噪音点
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()));
}
//画图片的边框线
g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
System.IO.MemoryStream ms = new System.IO.MemoryStream();
image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
Response.ClearContent();
Response.ContentType = "image/Gif";
Response.BinaryWrite(ms.ToArray());
}
finally
{
g.Dispose();
image.Dispose();
}
}
string[] str = new string[4];
string serverCode = "";
//生成随机生成器
Random random = new Random();
for (int i = 0; i < 4; i++)
{
str[i] = random.Next(10).ToString().Substring(0, 1);
}
CreateCheckCodeImage(str);
foreach (string s in str)
{
serverCode += s;
}
Session["serverCode"] = serverCode;
}
private void CreateCheckCodeImage(string[] checkCode)
{
if (checkCode == null || checkCode.Length <= 0)
return;
System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 32.5)), 30);
System.Drawing.Graphics g = Graphics.FromImage(image);
try
{
Random random = new Random();
//清空图片背景色
g.Clear(Color.White);
//画图片的背景噪音线
for (int i = 0; i < 20; 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);
}
//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[] f = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" };
for (int k = 0; k <= checkCode.Length - 1; k++)
{
int cindex = random.Next(7);
int findex = random.Next(5);
Font drawFont = new Font(f[findex], 16, (System.Drawing.FontStyle.Bold));
SolidBrush drawBrush = new SolidBrush(c[cindex]);
float x = 5.0F;
float y = 0.0F;
float width = 20.0F;
float height = 25.0F;
int sjx = random.Next(10);
int sjy = random.Next(image.Height - (int)height);
RectangleF drawRect = new RectangleF(x + sjx + (k * 25), y + sjy, width, height);
StringFormat drawFormat = new StringFormat();
drawFormat.Alignment = StringAlignment.Center;
g.DrawString(checkCode[k], drawFont, drawBrush, drawRect, drawFormat);
}
//画图片的前景噪音点
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()));
}
//画图片的边框线
g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
System.IO.MemoryStream ms = new System.IO.MemoryStream();
image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
Response.ClearContent();
Response.ContentType = "image/Gif";
Response.BinaryWrite(ms.ToArray());
}
finally
{
g.Dispose();
image.Dispose();
}
}
下一步就是使用这个验证码了。html如下
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="RegisterUser.aspx.cs" Inherits="JackdeskNoteWebForm.User.RegisterUser" %>
<!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>用户注册</title>
<script type="text/javascript" src="/FormValidator/jquery-1.4.1.min.js"></script>
<script type="text/javascript">
function aa() {
$("#image1").attr('src','../Img.aspx?'+Math.random());
}
</script>
</head>
<body>
<div id="wrap">
<form id="form2" runat="server">
<div id="container1" style="height:300px">
<fieldset style="text-align: left">
<legend id="Legend1">用户注册</legend>
<table border="0" cellspacing="0" cellpadding="0" width="550px">
<tr>
<td class="tdright">
验证图片：
</td>
<td>
<img src="../Img.aspx" id="image1" alt="" onclick="aa()" title="看不清换一张" />
</td>
<td class="tdwidth">
<a href="javascript:aa()">看不清楚</a> <span id="Span1" style="width: 200px"></span>
</td>
</tr>
<tr>
<td class="tdright">
验证码：
</td>
<td>
<asp:TextBox ID="tbxCode" runat="server"></asp:TextBox>
</td>
<td class="tdwidth">
</td>
</tr>
</table>
</fieldset>
</div>
</form>
</div>
</body>
<!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>用户注册</title>
<script type="text/javascript" src="/FormValidator/jquery-1.4.1.min.js"></script>
<script type="text/javascript">
function aa() {
$("#image1").attr('src','../Img.aspx?'+Math.random());
}
</script>
</head>
<body>
<div id="wrap">
<form id="form2" runat="server">
<div id="container1" style="height:300px">
<fieldset style="text-align: left">
<legend id="Legend1">用户注册</legend>
<table border="0" cellspacing="0" cellpadding="0" width="550px">
<tr>
<td class="tdright">
验证图片：
</td>
<td>
<img src="../Img.aspx" id="image1" alt="" onclick="aa()" title="看不清换一张" />
</td>
<td class="tdwidth">
<a href="javascript:aa()">看不清楚</a> <span id="Span1" style="width: 200px"></span>
</td>
</tr>
<tr>
<td class="tdright">
验证码：
</td>
<td>
<asp:TextBox ID="tbxCode" runat="server"></asp:TextBox>
</td>
<td class="tdwidth">
</td>
</tr>
</table>
</fieldset>
</div>
</form>
</div>
</body>
</html>
验证码验证：
string checkCode = Session["serverCode"].ToString();
string getCode=tbxCode.Text.Trim();
if (getCode!=checkCode)
{
MessageBox.Show(this, "验证码错误");
string getCode=tbxCode.Text.Trim();
if (getCode!=checkCode)
{
MessageBox.Show(this, "验证码错误");
}
