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protectedvoid Page_Load(object sender, EventArgs e) { string[] str = new string[4]; string serverCode = ""; //生成随机生成器 Random random = new Random(); for (int i = 0; i < 4; i++) { str[i] = random.Next(10).ToString().Substring(0, 1); } CreateCheckCodeImage(str); foreach (string s in str) { serverCode += s; } Session["serverCode"] = serverCode; } private void CreateCheckCodeImage(string[] checkCode) { if (checkCode == null || checkCode.Length <= 0) return; System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 32.5)), 30); System.Drawing.Graphics g = Graphics.FromImage(image); try { 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 < 20; 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); } //定义颜色 Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple }; //定义字体 string[] f = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" }; for (int k = 0; k <= checkCode.Length - 1; k++) { int cindex = random.Next(7); int findex = random.Next(5); Font drawFont = new Font(f[findex], 16, (System.Drawing.FontStyle.Bold)); SolidBrush drawBrush = new SolidBrush(c[cindex]); float x = 5.0F; float y = 0.0F; float width = 20.0F; float height = 25.0F; int sjx = random.Next(10); int sjy = random.Next(image.Height - (int)height); RectangleF drawRect = new RectangleF(x + sjx + (k * 25), y + sjy, width, height); StringFormat drawFormat = new StringFormat(); drawFormat.Alignment = StringAlignment.Center; g.DrawString(checkCode[k], drawFont, drawBrush, drawRect, drawFormat); } //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); System.IO.MemoryStream ms = new System.IO.MemoryStream(); image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif); Response.ClearContent(); Response.ContentType = "image/Gif"; Response.BinaryWrite(ms.ToArray()); } finally { g.Dispose(); image.Dispose(); } }
页面
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="RegisterUser.aspx.cs" Inherits="JackdeskNoteWebForm.User.RegisterUser" %> <!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>用户注册</title> <script type="text/javascript" src="/FormValidator/jquery-1.4.1.min.js"></script> <script type="text/javascript"> function aa() { $("#image1").attr(‘src‘,‘../Img.aspx?‘+Math.random()); } </script> </head> <body> <div id="wrap"> <form id="form2" runat="server"> <div id="container1" style="height:300px"> <fieldset style="text-align: left"> <legend id="Legend1">用户注册</legend> <table border="0" cellspacing="0" cellpadding="0" width="550px"> <tr> <td class="tdright"> 验证图片： </td> <td> <img src="../Img.aspx" id="image1" alt="" onclick="aa()" title="看不清换一张" /> </td> <td class="tdwidth"> <a href="javascript:aa()">看不清楚</a> <span id="Span1" style="width: 200px"></span> </td> </tr> <tr> <td class="tdright"> 验证码： </td> <td> <asp:TextBox ID="tbxCode" runat="server"></asp:TextBox> </td> <td class="tdwidth"> </td> </tr> </table> </fieldset> </div> </form> </div> </body> </html>
验证
string checkCode = Session["serverCode"].ToString(); string getCode=tbxCode.Text.Trim(); if (getCode!=checkCode) { MessageBox.Show(this, "验证码错误"); }
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原文地址：http://www.cnblogs.com/lishuo/p/4546519.html
