public class ValidateCode : System.Web.UI.Page
{
private void Page_Load(object sender, System.EventArgs e)
{ this.CreateCheckCodeImage(GenerateCheckCode());
}
Web 窗体设计器生成的代码 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(); } }
}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 *****/ }效果：
在CheckCode.aspx的html的<head></head>中加入以下代码，后退验证码会刷新。
<% Response.Buffer = true ;%>
<% Response.ExpiresAbsolute = DateTime.Now.AddSeconds(-1);%>
<% Response.Expires = 0 ;%>
<% Response.CacheControl = "no-cache" ; %>
