易学网图片验证码设计与使用(C#原代码)

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为防止暴力注册提交数据，设计图片验证码成为必要。
之前用Label存储如"1+3=?"不可取，因用document.getIdByElement()可以获取到答案，成为掩耳盗铃，此地无银300两之举措。现在改成图片验证且编码保存在Session内破解难度就大了!

源代码如下:
1.生成图片验证码的类(业务类)

Code
using System;
using System.Data;
using System.Web;
using System.Drawing;
using System.Web.UI;
using System.Web.UI.WebControls;
using vjsdn.globals;
using System.Drawing.Drawing2D;

namespace vjsdn.SystemSecurityLibrary
{
   /// <summary>
   /// 生成图片验证码
   /// </summary>
   public class CGenValidateCode
   {
      #region 随机字符验证码

      private Page _page = null;
      public CGenValidateCode(Page page)
      {
         _page = page;
      }

      /// <summary>
      /// 产生验证码
      /// </summary>
      /// <returns></returns>
      private string CreateCode(int codeLength)
      {
         string chars = "1,2,3,4,5,6,7,8,9,0,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z," +
         "A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z";
         string[] strArr = chars.Split(’,’);
         string code = "";
         Random rand = new Random();
         for (int i = 0; i < codeLength; i++)
         {
            code += strArr[rand.Next(0, strArr.Length)];
         }
         return code;
      }

      /// <summary>
      /// 输出验证图片
      /// </summary>
      /// <param name="code"></param>
      private void CreateImage(string code)
      {
         Bitmap image = new Bitmap(70, 20); //验证码图片模块
         Graphics g = Graphics.FromImage(image);
         WebColorConverter ww = new WebColorConverter();
         g.Clear((Color)ww.ConvertFromString("#dadada")); //底色

         Random random = new Random();

         //画图片的背景噪音线
         for (int i = 0; i < 12; 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.LightGray), x1, y1, x2, y2);
         }

         //验证码字体
         Font font = new Font("arial", 13, FontStyle.Bold | FontStyle.Italic);

         //画笔对象
         LinearGradientBrush brush = new LinearGradientBrush(
         new Rectangle(0, 0, image.Width, image.Height), Color.Red, Color.Gray, 1.2f, true);
         g.DrawString(code, font, brush, 0, 0);

         //画图片的前景噪音点
         for (int i = 0; i < 10; i++)
         {
            int x = random.Next(image.Width);
            int y = random.Next(image.Height);
            image.SetPixel(x, y, Color.White);
         }

         //画图片的边框线
         g.DrawRectangle(new Pen(Color.Gray), 0, 0, image.Width - 1, image.Height - 1);

         System.IO.MemoryStream ms = new System.IO.MemoryStream();
         image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
         _page.Response.ClearContent();
         _page.Response.ContentType = "image/Gif"; //HTTP MIME TYPE 设为图片输出
         _page.Response.BinaryWrite(ms.ToArray());
         g.Dispose();
         image.Dispose();
      }

      /// <summary>
      /// 生成新的验证码
      /// </summary>
      public void Generate()
      {
         string checkCode = this.CreateCode(5); //生成新的验证码
         _page.Session["_MyCode"] = checkCode;
         this.CreateImage(checkCode);
      }

      /// <summary>
      /// 检验用户输入的验证码
      /// </summary>
      /// <param name="validatePage">要验证的页面</param>
      /// <param name="input">用户输入的验证码</param>
      /// <returns></returns>
      public static bool ValidateLastCode(Page validatePage, string input)
      {
         //将对象转换为字符串
         string lastCode = Convert.ToString(validatePage.Session["_MyCode"]);
         return (input.ToUpper() == lastCode.ToUpper());
      }

      #endregion
   }

}

2.编写CreateValidateImg.aspx页面,用来生成图片。代码很少,在Page_Load事件内创建对象就行了!

Code
public partial class CreateValidateImg : System.Web.UI.Page
{
   private CGenValidateCode _gen = null;

   protected void Page_Load(object sender, EventArgs e)
   {
      _gen = new CGenValidateCode(this);
      _gen.Generate();
   }
}

3. 验证码应用,比如系统登录.

HTML Code 图片链接地址:
<img id="vcode" alt="" src="CreateValidateImg.aspx" />
如果产生的验证码看不清楚，加下面这段代码. getTime函数用来避免只能点一次链接。

<a href="#" οnclick="document.getElementById(’vcode’).src=’CreateValidateImg.aspx?temp=’+
( new Date().getTime().toString(36)); return false;">重新生成验证码</a>

C# Code 登录按钮Click事件

Code
protected void btnLogin_Click(object sender, EventArgs e)
{
   //在Login按钮内检查验证码,TextBox1.Text为用户输入的验证码,
   //通过类方法检查验证码.
   bool ret = CGenValidateCode.ValidateLastCode(this, TextBox1.Text);
   if (ret)
   this.Response.Write("用户输入验证码正确");
   else
   this.Response.Write("用户输入验证码错误");
}

有图为证: