怎么使用ASP.NET實(shí)現(xiàn)生成驗(yàn)證碼功能

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生成驗(yàn)證碼原理：產(chǎn)生隨機(jī)字符，并將字符生成為圖片，同時(shí)儲(chǔ)存到Session里去，然后驗(yàn)證用戶輸入的內(nèi)容是否與Session中的驗(yàn)證碼相符即可。

一般處理程序：CheckCodeHandler.cs

<%@ WebHandler Language="C#" Class="CheckCodeHandler" %>
using System;
using System.Web;
using System.Text;
using System.Drawing;
using System.Web.SessionState;
public class CheckCodeHandler : IHttpHandler,IRequiresSessionState
{
  //產(chǎn)生驗(yàn)證碼的字符集
  public string charcode = "2,3,4,5,6,8,9,A,B,C,D,E,F,G,H,J,K,M,N,P,R,S,U,W,X,Y,a,b,c,d,e,f,g,h,j,k,m,n,p,r,s,u,w,x,y";
  public void ProcessRequest (HttpContext context) {
    string validateCode = CreateRandomCode(4);
    context.Session["ValidateCode"] = validateCode;//將驗(yàn)證碼保存到session中
    CreateCodeImage(validateCode, context);
  }
  public bool IsReusable {
    get {
      return false;
    }
  }
  /// <summary>
  /// 生成驗(yàn)證碼
  /// </summary>
  /// <param name="n">驗(yàn)證碼個(gè)數(shù)</param>
  /// <returns>驗(yàn)證碼字符串</returns>
  public string CreateRandomCode(int n)
  {
    string[] CharArray = charcode.Split(',');//將字符串轉(zhuǎn)換為字符數(shù)組
    string randomCode = "";
    int temp = -1;
    Random rand = new Random();
    for (int i = 0; i < n; i++)
    {
      if (temp != -1)
      {
        rand = new Random(i * temp * ((int)DateTime.Now.Ticks));
      }
      int t = rand.Next(CharArray.Length - 1);
      if (temp != -1 && temp == t)
      {
        return CreateRandomCode(n);
      }
      temp = t;
      randomCode += CharArray[t];
    }
    return randomCode;
  }
  public void CreateCodeImage(string checkCode, HttpContext context)
  {
    int iwidth = (int)(checkCode.Length * 13);
    System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 20);
    Graphics g = Graphics.FromImage(image);
    Font f = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Italic | System.Drawing.FontStyle.Bold));
    // 前景色
    Brush b = new System.Drawing.SolidBrush(Color.Black);
    // 背景色
    g.Clear(Color.White);
    // 填充文字
    g.DrawString(checkCode, f, b, 0, 1);
    // 隨機(jī)線條
    Pen linePen = new Pen(Color.Gray, 0);
    Random rand = new Random();
    for (int i = 0; i < 5; i++)
    {
      int x1 = rand.Next(image.Width);
      int y1 = rand.Next(image.Height);
      int x2 = rand.Next(image.Width);
      int y2 = rand.Next(image.Height);
      g.DrawLine(linePen, x1, y1, x2, y2);
    }
    // 隨機(jī)點(diǎn)
    for (int i = 0; i < 30; i++)
    {
      int x = rand.Next(image.Width);
      int y = rand.Next(image.Height);
      image.SetPixel(x, y, Color.Gray);
    }
    // 邊框
    g.DrawRectangle(new Pen(Color.Gray), 0, 0, image.Width - 1, image.Height - 1);
    // 輸出圖片
    System.IO.MemoryStream ms = new System.IO.MemoryStream();
    image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
    context.Response.ClearContent();
    context.Response.ContentType = "image/jpeg";
    context.Response.BinaryWrite(ms.ToArray());
    g.Dispose();
    image.Dispose();
  }
}

封裝成類庫：ValidateNumber.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Drawing;
using System.Web.UI;
using System.Drawing.Drawing2D;
using System.IO;
using System.Drawing.Imaging;
/// <summary>
///ValidateNumber 生成驗(yàn)證碼
/// </summary>
public class ValidateNumber
{
  //產(chǎn)生驗(yàn)證碼的字符集 （易混淆的字符去掉）
  private string charcode = "2,3,4,5,6,8,9,A,B,C,D,E,F,G,H,J,K,M,N,P,R,S,U,W,X,Y,a,b,c,d,e,f,g,h,j,k,m,n,p,r,s,u,w,x,y";
  /// <summary>
  /// 驗(yàn)證碼的最大長(zhǎng)度
  /// </summary>
  public int MaxLength
  {
    get { return 10; }
  }
  /// <summary>
  /// 驗(yàn)證碼的最小長(zhǎng)度
  /// </summary>
  public int MinLength
  {
    get { return 1; }
  }
  /// <summary>
  /// 生成驗(yàn)證碼
  /// </summary>
  /// <param name="length">指定驗(yàn)證碼的長(zhǎng)度</param>
  /// <returns></returns>
  public string CreateValidateNumber(int length)
  {
    string[] CharArray = charcode.Split(',');//將字符串轉(zhuǎn)換為字符數(shù)組
    string randomCode = "";
    int temp = -1;
    Random rand = new Random();
    for (int i = 0; i < length; i++)
    {
      if (temp != -1)
      {
        rand = new Random(i * temp * ((int)DateTime.Now.Ticks));
      }
      int t = rand.Next(CharArray.Length - 1);
      if (temp != -1 && temp == t)
      {
        return CreateValidateNumber(length);
      }
      temp = t;
      randomCode += CharArray[t];
    }
    return randomCode;
  }
  /// <summary>
  /// 創(chuàng)建驗(yàn)證碼的圖片
  /// </summary>
  /// <param name="context">context對(duì)象</param>
  /// <param name="validateNum">驗(yàn)證碼</param>
  public void CreateValidateGraphic(HttpContext context,string validateNum)
  {
    int iwidth = (int)(validateNum.Length * 14);
    Bitmap image = new Bitmap(iwidth, 22);
    Graphics g = Graphics.FromImage(image);
    try
    {
      //生成隨機(jī)生成器
      Random random = new Random();
      //清空?qǐng)D片背景色
      g.Clear(Color.White);
      //畫圖片的干擾線
      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(validateNum, font, brush, 3, 2);
      //畫圖片的前景干擾點(diǎn)
      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()));
      }
      //畫圖片的邊框線
      g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
      //保存圖片數(shù)據(jù)
      MemoryStream stream = new MemoryStream();
      image.Save(stream, ImageFormat.Jpeg);
      //輸出圖片
      context.Response.Clear();
      context.Response.ContentType = "image/jpeg";
      context.Response.BinaryWrite(stream.ToArray());
    }
    finally
    {
      g.Dispose();
      image.Dispose();
    }
  }
  /// <summary>
  /// 得到驗(yàn)證碼圖片的長(zhǎng)度
  /// </summary>
  /// <param name="validateNumLength">驗(yàn)證碼的長(zhǎng)度</param>
  /// <returns></returns>
  public static int GetImageWidth(int validateNumLength)
  {
    return (int)(validateNumLength * 14);
  }
  /// <summary>
  /// 得到驗(yàn)證碼圖片的高度
  /// </summary>
  /// <returns></returns>
  public static double GetImageHeight()
  {
    return 22;
  }
}

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