ASP.NET中无刷新验证码实现(http://www.diybl.com/course/4_webprogram/asp.net/asp_netxl/20081022/150959

本文介绍了一种在ASP.NET中实现无刷新验证码的方法。通过使用JavaScript动态更新图片源的方式，确保验证码每次点击都能刷新，而无需整个页面重新加载。代码示例展示了如何生成随机验证码字符串并将其显示为图片。

ASP.NET中无刷新验证码实现

Default.aspx页面代码 <%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head runat="server"> <title>Untitled Page</title> <script>function show(im) { im.src="Default2.aspx?"+new Date;//注意这里的new Date一定要加上，否则只会生成一次验证码 }</script> </head> <body> <form id="form1" runat="server"> <div> <img src="Default2.aspx" onclick ="show(this)" /> </div> </form> </body> </html>

Default2.cs代码主要用来生成验证图片
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; public partial class Default2 : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { CreateCheckCodeImage(GenerateCheckCode()); } /// <summary> /// 生成随机校验码字符串 /// </summary> /// <returns>生成的随机校验码字符串</returns> public string GenerateCheckCode() { int number; string strCode = string.Empty; //随机数种子 Random radom = new Random(); for (int i = 0; i < 4; i++) { //随机的整数 number = radom.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中保存校验码或Session中 Response.Cookies.Add(new HttpCookie("CheckCode", strCode)); return strCode; } /// <summary> /// 根据校验码输出图片 /// </summary> /// <param name="checkCode">产生的随机校验码</param> public 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(decimal.Parse((checkCode.Length * 15)+"")), 20); //创建ＧＲＡＰＨＩＣＳ对象 System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(image); try { //生成随机数种子 Random random = new Random(); //清空图片背景色 g.Clear(System.Drawing.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); //用银色画出噪音线 g.DrawLine(new System.Drawing.Pen (System.Drawing.Color.Silver), x1, y1, x2, y2); } //输出图片中校验码的字体：１２号Arial,粗斜体 System.Drawing.Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic)); //线形渐变画刷 System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new System.Drawing.Rectangle(0, 0, image.Width, image.Height), System.Drawing.Color.Blue, System.Drawing.Color.Purple, 1.2f, true); g.DrawString(checkCode, font, brush, 2, 3); //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, System.Drawing.Color.FromArgb(random.Next())); } //画图片的边框线 g.DrawRectangle(new System.Drawing.Pen(System.Drawing.Color.SaddleBrown), 0, 0, image.Width - 1, image.Height - 1); //创建内存流用于输出图片 using (System.IO.MemoryStream ms = new System.IO.MemoryStream()) { //图片格式指定为ＰＮＧ image.Save(ms, System.Drawing.Imaging.ImageFormat.Png); //清除缓冲区流中的所有输出 Response.ClearContent(); //输出流的ＨＴＴＰＭＩＭＥ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(); } } }