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C#实现验证码

2006-05-29 10:25 387 查看

public class ValidateCode : System.Web.UI.Page
{
private void Page_Load(object sender, System.EventArgs e)
{
this.CreateCheckCodeImage(GenerateCheckCode());
} #region Web 窗体设计器生成的代码
override protected void OnInit(EventArgs e)
{
//
// CODEGEN: 该调用是 ASP.NET Web 窗体设计器所必需的。
//
InitializeComponent();
base.OnInit(e);
}

/// <summary>
/// 设计器支持所需的方法 - 不要使用代码编辑器修改
/// 此方法的内容。
/// </summary>
private void InitializeComponent()
{
this.Load += new System.EventHandler(this.Page_Load);
}
#endregion
private string GenerateCheckCode()
{
int number;
char code;
string checkCode = String.Empty;
System.Random random = new Random();
for(int i=0; i<5; i++)
{
number = random.Next();
if(number % 2 == 0)
code = (char)('0' + (char)(number % 10));
else
code = (char)('A' + (char)(number % 26));
checkCode += code.ToString();
}
Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));
return checkCode;
}
private void CreateCheckCodeImage(string checkCode)
{
if(checkCode == null || checkCode.Trim() == String.Empty)
return;
System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 22);
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);
//画图片的背景噪音线
for(int i=0; i<25; 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 System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
g.DrawString(checkCode, font, brush, 2, 2);
//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();
}
}
}

　　假如以上验证码生成器页面名为：CheckCode.aspx，那么在登录页面中使用“<IMG>” 这个 HTML 元素来显示生成的验证码图片：<IMG src="CheckCode.aspx">
　　在登录页面的登录按钮的处理事件中使用以下代码判断验证码：
private void btnLogin_Click(object sender, System.Web.UI.ImageClickEventArgs e)
{
if(Request.Cookies["CheckCode"] == null)
{
lblMessage.Text = "您的浏览器设置已被禁用 Cookies，您必须设置浏览器允许使用 Cookies 选项后才能使用本系统。";
lblMessage.Visible = true;
return;
} if(String.Compare(Request.Cookies["CheckCode"].Value, txtCheckCode.Text, true) != 0)
{
lblMessage.Text = "验证码错误，请输入正确的验证码。";
lblMessage.Visible = true;
return;
}

}

第二種方法一樣也是可以實現驗証碼

前台CheckCode.aspx

<%@ Page language="c#" Inherits="Guestbook.CheckCode" CodeFile="CheckCode.aspx.cs" %>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >

<HTML>

<HEAD>

<title>CheckCode</title>

</HEAD>

<body>

</form>

</body>

</HTML>

后台CheckCode.aspx.cs

using System;

using System.Collections;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Web;

using System.Web.SessionState;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.Web.UI.HtmlControls;

namespace Guestbook

{

/// <summary>

/// 页面检查生成的Session["CheckCode"]

/// </summary>

public partial class CheckCode : System.Web.UI.Page

{

protected void Page_Load(object sender, System.EventArgs e)

{

this.CreateCheckCodeImage(GenerateCheckCode());

}

private string GenerateCheckCode()

{

int number;

char code;

string checkCode = String.Empty;

System.Random random = new Random();

for(int i=0; i<5; i++)

{

number = random.Next();

if(number % 2 == 0)

code = (char)('0' + (char)(number % 10));

else

code = (char)('A' + (char)(number % 26));

checkCode += code.ToString();

}

//Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));

Session["CheckCode"]=checkCode;

return checkCode;

}

private void CreateCheckCodeImage(string checkCode)

{

if(checkCode == null || checkCode.Trim() == String.Empty)

return;

System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 22);

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);

//画图片的背景噪音线

for(int i=0; i<25; 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 System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));

System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);

g.DrawString(checkCode, font, brush, 2, 2);

//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();

}

-----------------------------------
调用页面Default.aspx

<tr>

<input onclick="document.getElementById('CodeImg').src='CheckCode.aspx?tmp='+Math.random()"

type="button" value="验证码" name="Btn_Re" /></td>

</tr>
之后在后台对Session["CheckCode"].ToString().ToLower()进行验证就行了，来判断验证码是否正确。
希望对大家有帮助

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