本文介绍了一个基于 ASP.NET 的简单验证码生成方法，通过 C# 编程实现了验证码的生成、图片绘制及存储过程。该方法利用了随机数生成字母和数字组合，并通过 Session 存储验证码内容。
defalut.aspx的前台代码：
<script type="text/javascript">google_ad_client = "pub-2048279401139630";google_ad_slot = "8856771542";google_ad_width = 728;google_ad_height = 90;document.write("<s"+"cript type='text/javascript' s"+"rc='http://pagead2.googlesyndication.com/pagead/show_ads"+"."+"js'></scr"+"ipt>");</script>
<%...@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>无标题页</title>
</head>
<body>
<form id="form1" runat="server">
<div>
</div>
</form>
</body>
</html>
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");
using System;
using System.Data;
using System.Configuration;
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;
public partial class _Default : System.Web.UI.Page
...{
protected void Page_Load(object sender, EventArgs e)
...{
OTC.Utility.ValidateCodeHelper.CreateRandomCode(4);
}
}
核心代码ValidateCodeHelper.cs如下：
using System;
using System.Collections.Generic;
using System.Text;
using System.Web;
using System.Web.UI;
using System.Drawing;
namespace OTC.Utility
...{
public sealed class ValidateCodeHelper
...{
/**//// <summary>
/// 生成随机码
/// </summary>
/// <param name="length">随机码个数</param>
public static void CreateRandomCode(int length)
...{
CreateRandomCode("ValidateCode", length);
}
/**//// <summary>
/// 生成随机码
/// </summary>
/// <param name="strSessionName">session的名称</param>
/// <param name="length">随机码个数</param>
/// <returns></returns>
public static void CreateRandomCode(string strSessionName,int length)
...{
int rand;
char code;
string randomcode = String.Empty;
//生成一定长度的验证码
System.Random random = new Random();
for (int i = 0; i < length; i++)
...{
rand = random.Next();
if (rand % 3 == 0)
...{ code = (char)('A' + (char)(rand % 26)); }
else
...{ code = (char)('0' + (char)(rand % 10)); }
randomcode += code.ToString();
}
HttpContext.Current.Session[strSessionName] = randomcode;
//ViewState["ValidateCode"] = randomcode;
CreateImage(randomcode);
}
/**//// <summary>
/// 创建随机码图片
/// </summary>
/// <param name="randomcode">随机码</param>
private static void CreateImage(string randomcode)
...{
int randAngle = 45; //随机转动角度
int mapwidth = (int)(randomcode.Length * 22);
Bitmap map = new Bitmap(mapwidth, 28); //创建图片背景
Graphics graph = Graphics.FromImage(map);
//Font fontstyle = new Font("Arial", 20, FontStyle.Bold); //字体样式
//graph.FillRectangle(new SolidBrush(Color.Black), 0, 0, map.Width+1, map.Height+1); //填充一个有背景的矩形
graph.Clear(Color.AliceBlue); //清除画面，填充背景
//graph.DrawRectangle(new Pen(Color.Black, 0), 0, 0, map.Width - 1, map.Height - 1); //画一个边框
//graph.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias; //模式
Random rand = new Random();
//画图片的背景噪音线
for (int i = 0; i < 25; i++)
...{
int x1 = rand.Next(map.Width);
int x2 = rand.Next(map.Width);
int y1 = rand.Next(map.Height);
int y2 = rand.Next(map.Height);
graph.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
}
//验证码旋转，防止机器识别
char[] chars = randomcode.ToCharArray(); //拆散字符串成单字符数组
//文字距中
StringFormat format = new StringFormat(StringFormatFlags.NoClip);
format.Alignment = StringAlignment.Center;
format.LineAlignment = StringAlignment.Center;
for (int i = 0; i < chars.Length; i++)
...{
Font fontstyle = new Font("Arial", rand.Next(20, 22), FontStyle.Regular); //字体样式
Point dot = new Point(16, 16);
//graph.DrawString(dot.X.ToString(), fontstyle, new SolidBrush(Color.Black), 10, 150); //测试X坐标显示间距的
float angle = rand.Next(-randAngle, randAngle); //转动的度数
graph.TranslateTransform(dot.X, dot.Y); //移动光标到指定位置
graph.RotateTransform(angle);
graph.DrawString(chars[i].ToString(), fontstyle, new SolidBrush(Color.Blue), 1, 1, format);
graph.RotateTransform(-angle); //转回去
graph.TranslateTransform(2, -dot.Y); //移动光标到指定位置
}
//graph.DrawString(randomcode, fontstyle, new SolidBrush(Color.Blue), 2, 2); //标准随机码
//画图片的前景噪音点
for (int i = 0; i < 100; i++)
...{
int x = rand.Next(map.Width);
int y = rand.Next(map.Height);
map.SetPixel(x, y, Color.FromArgb(rand.Next()));
}
//生成图片
System.IO.MemoryStream ms = new System.IO.MemoryStream();
map.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
HttpContext.Current.Response.ClearContent();
HttpContext.Current.Response.ContentType = "image/gif";
HttpContext.Current.Response.BinaryWrite(ms.ToArray());
graph.Dispose();
map.Dispose();
}
}
![](https:<script%20type="text/javascript">google_ad_client%20=%20"pub-2048279401139630";google_ad_slot%20=%20"8856771542";google_ad_width%20=%20728;google_ad_height%20=%2090;document.write%28"<s"+"cript%20type='text/javascript'%20s"+"rc='http://pagead2.googlesyndication.com/pagead/show_ads"+"."+"js'></scr"+"ipt>"%29;</script>oogle_ad_client%20=)
");
<%...@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" ><head runat="server"> <title>无标题页</title></head><body> <form id="form1" runat="server"> <div> </div> </form></body></html>defalut.aspx的后台代码default.aspx.cs如下：
using System;using System.Data;using System.Configuration;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;public partial class _Default : System.Web.UI.Page ...{ protected void Page_Load(object sender, EventArgs e) ...{ OTC.Utility.ValidateCodeHelper.CreateRandomCode(4); }}核心代码ValidateCodeHelper.cs如下：
using System;using System.Collections.Generic;using System.Text;using System.Web;using System.Web.UI;using System.Drawing;namespace OTC.Utility...{ public sealed class ValidateCodeHelper ...{ /**//// <summary> /// 生成随机码 /// </summary> /// <param name="length">随机码个数</param> public static void CreateRandomCode(int length) ...{ CreateRandomCode("ValidateCode", length); } /**//// <summary> /// 生成随机码 /// </summary> /// <param name="strSessionName">session的名称</param> /// <param name="length">随机码个数</param> /// <returns></returns> public static void CreateRandomCode(string strSessionName,int length) ...{ int rand; char code; string randomcode = String.Empty; //生成一定长度的验证码 System.Random random = new Random(); for (int i = 0; i < length; i++) ...{ rand = random.Next(); if (rand % 3 == 0) ...{ code = (char)('A' + (char)(rand % 26)); } else ...{ code = (char)('0' + (char)(rand % 10)); } randomcode += code.ToString(); } HttpContext.Current.Session[strSessionName] = randomcode; //ViewState["ValidateCode"] = randomcode; CreateImage(randomcode); } /**//// <summary> /// 创建随机码图片 /// </summary> /// <param name="randomcode">随机码</param> private static void CreateImage(string randomcode) ...{ int randAngle = 45; //随机转动角度 int mapwidth = (int)(randomcode.Length * 22); Bitmap map = new Bitmap(mapwidth, 28); //创建图片背景 Graphics graph = Graphics.FromImage(map); //Font fontstyle = new Font("Arial", 20, FontStyle.Bold); //字体样式 //graph.FillRectangle(new SolidBrush(Color.Black), 0, 0, map.Width+1, map.Height+1); //填充一个有背景的矩形 graph.Clear(Color.AliceBlue); //清除画面，填充背景 //graph.DrawRectangle(new Pen(Color.Black, 0), 0, 0, map.Width - 1, map.Height - 1); //画一个边框 //graph.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias; //模式 Random rand = new Random(); //画图片的背景噪音线 for (int i = 0; i < 25; i++) ...{ int x1 = rand.Next(map.Width); int x2 = rand.Next(map.Width); int y1 = rand.Next(map.Height); int y2 = rand.Next(map.Height); graph.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2); } //验证码旋转，防止机器识别 char[] chars = randomcode.ToCharArray(); //拆散字符串成单字符数组 //文字距中 StringFormat format = new StringFormat(StringFormatFlags.NoClip); format.Alignment = StringAlignment.Center; format.LineAlignment = StringAlignment.Center; for (int i = 0; i < chars.Length; i++) ...{ Font fontstyle = new Font("Arial", rand.Next(20, 22), FontStyle.Regular); //字体样式 Point dot = new Point(16, 16); //graph.DrawString(dot.X.ToString(), fontstyle, new SolidBrush(Color.Black), 10, 150); //测试X坐标显示间距的 float angle = rand.Next(-randAngle, randAngle); //转动的度数 graph.TranslateTransform(dot.X, dot.Y); //移动光标到指定位置 graph.RotateTransform(angle); graph.DrawString(chars[i].ToString(), fontstyle, new SolidBrush(Color.Blue), 1, 1, format); graph.RotateTransform(-angle); //转回去 graph.TranslateTransform(2, -dot.Y); //移动光标到指定位置 } //graph.DrawString(randomcode, fontstyle, new SolidBrush(Color.Blue), 2, 2); //标准随机码 //画图片的前景噪音点 for (int i = 0; i < 100; i++) ...{ int x = rand.Next(map.Width); int y = rand.Next(map.Height); map.SetPixel(x, y, Color.FromArgb(rand.Next())); } //生成图片 System.IO.MemoryStream ms = new System.IO.MemoryStream(); map.Save(ms, System.Drawing.Imaging.ImageFormat.Gif); HttpContext.Current.Response.ClearContent(); HttpContext.Current.Response.ContentType = "image/gif"; HttpContext.Current.Response.BinaryWrite(ms.ToArray()); graph.Dispose(); map.Dispose(); } }
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