ASP.net 验证码，C#

/* Copyright all(c) 2005 ZhongFeng, http://blog.csdn.net/SW515 */

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;

}

/*****其他代码 *****/

}