1.把这个生成验证码的类Validatenumimage加入项目中,类代码如下:
using System; 
using System.Drawing; using System.Drawing.Imaging; using System.IO; using System.Drawing.Drawing2D; using System.Web; using System.Web.UI; 
using System.Web.SessionState; /// ///图片验证码 /// public class Validatenumimage { 
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(); 
} //将生成的验证码加入Session中 HttpContext.Current.Session.Add("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); HttpContext.Current.Response.ClearContent(); HttpContext.Current.Response.ContentType = "image/Gif"; HttpContext.Current.Response.BinaryWrite(ms.ToArray()); } finally { g.Dispose(); image.Dispose(); } } public void CreateCheckCodeImage() { CreateCheckCodeImage(GenerateCheckCode()); } }2.再新建一个空ASPX页面MarkCheckCode.aspx;
3.在该页面的Page_Load事件里面调用该Validatenumimage类的方法：
protected void Page_Load(object sender, EventArgs e) { Validatenumimage markCheckCode = new Validatenumimage(); markCheckCode.CreateCheckCodeImage(); }4.在要使用验证码的页面里加入该标记;
<div>效果图预览:
