本文執行個體講述了asp.net使用ashx產生圖形驗證碼的方法。分享給大家供大家參考，具體如下：
驗證碼的好處不用我多說，你們都懂的。我在網上看到有人把驗證碼直接寫在aspx頁面裡，也就是說這種方式請求驗證碼等於請求一個頁面，這樣做很不科學。如下所示
<form id="form1" runat="server"> <p> <asp:Image ID="Image1" runat="server" ImageUrl="Default.aspx" /> <br /> <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox> <asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Button" /> </p></form>
這個代碼看著就覺得寫代碼的人比較欠揍，代碼寫成這樣子著實鬱悶。驗證嗎也不寫點script做下切換。
下面我介紹一種方式來實現這樣的功能
1. 寫個ashx產生圖形驗證碼
using System;using System.Collections;using System.Data;using System.Linq;using System.Web;using System.Web.Services;using System.Web.Services.Protocols;using System.Xml.Linq;using System.Web.SessionState;using System.Drawing;namespace usechecknum.ashx{ /// <summary> /// $codebehindclassname$ 的摘要說明 /// </summary> [WebService(Namespace = "http://tempuri.org/")] [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)] public class doCreateNum : IHttpHandler,IRequiresSessionState { public void ProcessRequest(HttpContext context) { context.Response.ContentType = "text/html"; string checkCode = GetValidation(5); // 產生5位隨機驗證碼字元 context.Session["Code"] = checkCode; //將字串儲存到Session中，以便需要時進行驗證 System.Drawing.Bitmap image = new System.Drawing.Bitmap(70, 22); Graphics g = Graphics.FromImage(image); try { //產生隨機產生器 Random random = new Random(); //清空圖片背景色 g.Clear(Color.White); // 畫圖片的背景雜音線 int i; for (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.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2F, true); g.DrawString(checkCode, font, brush, 2, 2); //畫圖片的前景噪音點 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); context.Response.ClearContent(); context.Response.ContentType = "image/Gif"; context.Response.BinaryWrite(ms.ToArray()); } finally { g.Dispose(); image.Dispose(); } } public string GetValidation(int num) { string str = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"; //"或者寫漢字也行" string validatecode = ""; Random rd = new Random(); for (int i = 0; i < num; i++) { validatecode += str.Substring(rd.Next(0, str.Length), 1); } return validatecode; } public bool IsReusable { get { return false; } } }}
2. 在頁面上顯示驗證碼，因為我們產生的是圖形，所以可以直接寫在<img/>標籤裡，我們只要寫段簡單的指令碼就可以點擊滑鼠切換驗證碼了
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="index.aspx.cs" Inherits="usechecknum._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>驗證碼的使用</title></head><script language="javascript" type="text/javascript"> function changeCode() { var imgNode = document.getElementById("vimg"); imgNode.src = "ashx/doCreateNum.ashx?t=" + (new Date()).valueOf(); // 這裡加個時間的參數是為了防止瀏覽器緩衝的問題 } </script><body> <form id="form1" runat="server"> 請輸入驗證碼:<input type="text" name="checknum"/><img src="ashx/doCreateNum.ashx" id="vimg" onclick="changeCode()" /> </form></body></html>
說了半天，該是時候看看產生的驗證碼長什麼樣了
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