生成随机验证码

摘录自《ASP.NET通用模块及典型系统开发实例导航》 求是科技，张蓓 著

 

创建RandomImage.aspx文件，前台不做任何添加，后台代码文件RandomImage.aspx.cs代码如下：

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.Drawing.Drawing2D; using System.IO; using System.Drawing.Imaging; namespace Book3 { public partial class RandomImage : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { CreateCheckCodeImage(GenerateCheckCode()); } /// <summary> /// 根据校验码输出图片 /// </summary> /// <param name="p"></param> private void CreateCheckCodeImage(string checkCode) { //若校验码为空，则直接返回 if (checkCode == null || checkCode.Trim() == string.Empty) { return; } //根据校验码的长度确定输出图片的长度 System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((double)(checkCode.Length * 15)), 20); //创建Graphics对象 Graphics g = Graphics.FromImage(image); try { //生成随机数种子 Random random = new Random(); //清空图片背景色 g.Clear(Color.White); //画图片的背景噪音线10条 for (int i = 0; i < 10; i++) { //噪音线起点坐标(x1,y1),终点坐标(x2,y2); 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); } //输出图片中校验码的字体：12号Arial,粗斜体 Font font = new Font( "Arial", 12, (FontStyle.Bold | FontStyle.Italic)); //线性渐变画刷 LinearGradientBrush brush = new LinearGradientBrush( new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.Purple, 1.2f, true); g.DrawString(checkCode, font, brush, 2, 2); //画图片的前景噪音点 50 个 for (int i = 0; i < 50; 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.SaddleBrown), 0, 0, image.Width - 1, image.Height - 1); //创建内存流用于输出图片 using (MemoryStream ms = new MemoryStream()) { //图片格式指定为Png image.Save(ms, ImageFormat.Png); //清除缓冲区流中的所有输出 Response.ClearContent(); //输出流的HTTP MIME类型设置为“image/png” Response.ContentType = "image/Png"; //输出图片的二进制流 Response.BinaryWrite(ms.ToArray()); } } finally { //释放Bitmap对象和Graphics对象 g.Dispose(); image.Dispose(); } } /// <summary> /// 生产随即校验码字符串 /// </summary> /// <returns>生产的随机校验码字符串</returns> private string GenerateCheckCode() { int number; string strCode = string.Empty; Random random=new Random(); //随机数种子 for (int i = 0; i < 4; i++)//校验码长度为4 { //随机的整数 number = random.Next(); //字符从0-9，A-Z中随机产生，对应的ASCII码分别为48-57,65-90 number = number % 36; if (number < 10) { number += 48; } else { number += 55; } strCode += ((char)number).ToString(); } //在Cookie中保存校验码 Response.Cookies.Add(new HttpCookie("CheckCode", strCode)); return strCode; } } }

在要使用验证码的页面添加一个Image控件，将“src”属性设置为上面创建的文件RandomImage.aspx。同时在对应的按钮中增加如下代码：

/判断Cookie是否为空，若为空，说明浏览器禁用了Cookie if (Request.Cookies["CheckCode"] == null) { lblMessage.Text = "您的浏览器色设置已禁用Cookie,您必须设置浏览器允许使用Cookies选项后才能使用本系统。"; lblMessage.Visible = true; return; } if (String.Compare(Request.Cookies["CheckCode"].Value, TextBox1.Text, true) != 0) { lblMessage.Text = "验证码错误，请输入正确的验证码。"; return; }