使用C#生成验证码图片，然后在网页中直接使用，很方便的用法。

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Web.UI;
using System.Drawing.Drawing2D;
using System.IO;/// <summary>
/// 生成验证码的类
/// </summary>
public class ValidateCode
{public ValidateCode(){}/// <summary>/// 验证码的最大长度/// </summary>public int MaxLength{get { return 10; }}/// <summary>/// 验证码的最小长度/// </summary>public int MinLength{get { return 1; }}/// <summary>/// 生成验证码/// </summary>/// <param name="length">指定验证码的长度</param>/// <returns></returns>public string CreateValidateCode(int length){int[] randMembers = new int[length];int[] validateNums = new int[length];string validateNumberStr = "";//生成起始序列值int seekSeek = unchecked((int)DateTime.Now.Ticks);Random seekRand = new Random(seekSeek);int beginSeek = (int)seekRand.Next(0, Int32.MaxValue - length * 10000);int[] seeks = new int[length];for (int i = 0; i < length; i++){beginSeek += 10000;seeks[i] = beginSeek;}//生成随机数字for (int i = 0; i < length; i++){Random rand = new Random(seeks[i]);int pownum = 1 * (int)Math.Pow(10, length);randMembers[i] = rand.Next(pownum, Int32.MaxValue);}//抽取随机数字for (int i = 0; i < length; i++){string numStr = randMembers[i].ToString();int numLength = numStr.Length;Random rand = new Random();int numPosition = rand.Next(0, numLength - 1);validateNums[i] = Int32.Parse(numStr.Substring(numPosition, 1));}//生成验证码for (int i = 0; i < length; i++){validateNumberStr += validateNums[i].ToString();}return validateNumberStr;}/// <summary>/// 创建验证码的图片/// </summary>/// <param name="containsPage">要输出到的page对象</param>/// <param name="validateNum">验证码</param>public byte[] CreateValidateGraphic(string validateCode){Bitmap image = new Bitmap((int)Math.Ceiling(validateCode.Length * 12.0), 24);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);//画图片的干扰线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 Font("Arial", 12, (FontStyle.Bold | FontStyle.Italic));LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height),Color.Blue, Color.DarkRed, 1.2f, true);g.DrawString(validateCode, font, brush, 3, 2);//画图片的前景干扰点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);//保存图片数据MemoryStream stream = new MemoryStream();image.Save(stream, ImageFormat.Jpeg);//输出图片流return stream.ToArray();}finally{g.Dispose();image.Dispose();}}/// <summary>/// 得到验证码图片的长度/// </summary>/// <param name="validateNumLength">验证码的长度</param>/// <returns></returns>public static int GetImageWidth(int validateNumLength){return (int)(validateNumLength * 12.0);}/// <summary>/// 得到验证码的高度/// </summary>/// <returns></returns>public static double GetImageHeight(){return 22.5;}
}本文转自齐师傅博客园博客，原文链接：http://www.cnblogs.com/youring2/archive/2013/04/03/2997859.html，如需转载请自行联系原作者