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></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></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 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

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