详解ASP.NET验证码的生成方法


一般验证码的生成方法都是相同的,主要的步骤都有两步

第一步:随机出一系统验证码的数字或字母,顺便把随机生成的数字或字母写入Cookies 或者 Session。

第二步:用第一步随机出来的数字或字母来合成图片。

可以看出来验证码的复杂度主要是第二步来完成,你可以根据自己所要的复杂度来设定。

我们一起来看看:

 第一步:随机生成数字或字母的方法

/// <summary>
  /// 生成验证码的随机数
  /// </summary>
  /// <returns>返回五位随机数</returns>
  private string GenerateCheckCode()
  {
    int number;
    char code;
    string checkCode = String.Empty;

    Random random = new Random();

    for (int i = 0; i < 5; i++)//可以任意设定生成验证码的位数
    {
      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));//写入COOKIS
    Session["CheckCode"] = checkCode; //写入Session,可以任意选一下
    return checkCode;
  }

第二步:生成图片

/// <summary>
  /// 生成验证码图片
  /// </summary>
  /// <param name="checkCode"></param>
  private void CreateCheckCodeImage(string checkCode)
  {
    if (checkCode == null || checkCode.Trim() == String.Empty)
      return;

    Bitmap image = new 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));
      LinearGradientBrush brush = new 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);

      MemoryStream ms = new MemoryStream();
      image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
      Response.ClearContent();
      Response.ContentType = "image/Gif";
      Response.BinaryWrite(ms.ToArray());
    }
    finally
    {//释放对象资源
      g.Dispose();
      image.Dispose();
    }

*完整程序

先在VS2005里面的项目里面添加一个 checkCode.aspx 文件,在checkCode.aspx.cs 代码文件中添加如下完整代码

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Drawing;
using System.IO;
using System.Drawing.Drawing2D;

public partial class checkCode : System.Web.UI.Page
{
  protected void Page_Load(object sender, EventArgs e)
  {
    CreateCheckCodeImage(GenerateCheckCode());//调用下面两个方法;
  }

  /// <summary>
  /// 生成验证码的随机数
  /// </summary>
  /// <returns>返回五位随机数</returns>
  private string GenerateCheckCode()
  {
    int number;
    char code;
    string checkCode = String.Empty;

    Random random = new Random();

    for (int i = 0; i < 5; i++)//可以任意设定生成验证码的位数
    {
      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));//写入COOKIS
    Session["CheckCode"] = checkCode; //写入Session,可以任意选一下
    return checkCode;
  }


  /// <summary>
  /// 生成验证码图片
  /// </summary>
  /// <param name="checkCode"></param>
  private void CreateCheckCodeImage(string checkCode)
  {
    if (checkCode == null || checkCode.Trim() == String.Empty)
      return;

    Bitmap image = new 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));
      LinearGradientBrush brush = new 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);

      MemoryStream ms = new MemoryStream();
      image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
      Response.ClearContent();
      Response.ContentType = "image/Gif";
      Response.BinaryWrite(ms.ToArray());
    }
    finally
    {//释放对象资源
      g.Dispose();
      image.Dispose();
    }
  }

}

上面生成验证码的页面都做好了,我们来调用看看:

在你需要用到验证码的地方加了Image控件

<asp:Image ID="Image1" runat="server" ImageUrl="~/checkCode.aspx" />

这样验证码就会显示到Image控件上面了!

显示弄好了,当然我们要判断一下用户的输入是否正确!

只要我们取得用户输入的值跟Cookis或者Session对比就OK了

取Cookies的值 Request.Cookies["CheckCode"].Value

取Session的值 Session["CheckCode"].ToString()    (最好先判断Session是否空)

如果不要区分大小写的话,就把用户输入的值和Cookies或Session的值都转成大写或都小写 

附用法

protected void Button1_Click(object sender, EventArgs e)
  {
    if (Request.Cookies["CheckCode"].Value == TextBox1.Text.Trim().ToString())
    {
      Response.Write("Cookies is right");
    }
    else
    {
      Response.Write("Cookies is wrong");
    }

    if (Session["CheckCode"] != null)
    {
      if (Session["CheckCode"].ToString().ToUpper() == TextBox1.Text.Trim().ToString().ToUpper())
        //这样写可以不能区分大小写
      {
        Response.Write("Session is right");

      }
      else
      {
        Response.Write("Session is wrong");
      }
    }
  }

以上就是本文的全部内容,教大家如何制作ASP.NET验证码,希望大家喜欢。


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