ASP.net 验证码(C#)

CreateImage.aspx.cs:

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.Drawing;

public partial class CreateImage : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
this.CreateCheckCodeImage(CreateCheckCode());

}
private string CreateCheckCode()
{
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();
}

}
}

Display.aspx

<img src="CreateImage.aspx"/>

Display.aspx.cs

Button事件：

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;
}

other data...
测试环境：VS.NET2005+WINXPSP2