在網上找了一個驗證碼的源代碼，使用後出現如下問題：不管你輸入正確與否，都會提示驗證碼錯誤。後來經過在qq羣裏和csdn發貼諮詢，得知是ie瀏覽器緩存問題。在經過他人的指點後改正了錯誤。源代碼如下：
-------------------Validate.aspx------------------
<%@ Page Language="C#" %>
<%@ import namespace="System"%>
<%@ import namespace="System.IO"%>
<%@ import namespace="System.Drawing"%>
<%@ import namespace="System.Drawing.Imaging"%>
<%@ import namespace="System.Drawing.Drawing2D"%>
<script runat="server">
private Bitmap validateimage;
private Graphics g;
public void Page_Load(object Sender ,EventArgs e ){
Response.BufferOutput = true; //特別注意
Response.Cache.SetExpires(DateTime.Now.AddMilliseconds(-1));//特別注意
Response.Cache.SetCacheability(HttpCacheability.NoCache);//特別注意
Response.AppendHeader("Pragma", "No-Cache"); //特別注意
string VNum =MakeValidateCode( );
Session["VNum"]=VNum;//取得驗證碼，以便後來驗證
ValidateCode(VNum);}
public void ValidateCode(string VNum)
{
validateimage = new Bitmap(60, 20, PixelFormat.Format24bppRgb);
g = Graphics.FromImage(validateimage);
g.FillRectangle(new LinearGradientBrush(new Point(0,0), new Point(110,20), Color.FromArgb(240,255,255,255),Color.FromArgb(240,255,255,255)),0,0,200,200);
g.DrawString(VNum, new Font("arial",11),new SolidBrush(Color.Red),new PointF(6,0));
g.Save();
MemoryStream ms=new MemoryStream();
validateimage.Save(ms,System.Drawing.Imaging.ImageFormat.Gif);
Response.ClearContent();
Response.ContentType="image/bmp";
Response.BinaryWrite(ms.ToArray());
Response.End();
}
string MakeValidateCode()
{
char[] s = new char[]{'0','1', '2','3','4','5','6','7','8','9','a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
string num = "";
Random r = new Random();
for(int i = 0; i < 5; i++)
{
num += s[r.Next(0, s.Length)].ToString();
}
return num;
}
</script>
-----------------------register.aspx------------
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Register.aspx.cs" Inherits="MyRegister.Register" %>
<!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>會員註冊</title>
<LINK href="stylesheet.css" _fcksavedurl=""stylesheet.css"" _fcksavedurl=""stylesheet.css"" _fcksavedurl=""stylesheet.css"" type="text/css" rel="stylesheet">
</head>
<body>
<form id="form1" runat="server">
<div class="middle" style="height: 1px" >
<div >
<asp:Label ID="UserName" runat="server" Text="用戶名：" ></asp:Label>
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
</div>
<div >
<asp:Label ID="UserPsw" runat="server" Text="密碼：" ></asp:Label>
<asp:TextBox ID="TextBox2" runat="server"></asp:TextBox></div>
<div >
<asp:Label ID="Label2" runat="server" Text="確認密碼：" ></asp:Label>
<asp:TextBox ID="TextBox6" runat="server"></asp:TextBox></div>
<div >
<asp:Label ID="Question" runat="server" Text="找回密碼問題："></asp:Label>
<asp:TextBox ID="TextBox3" runat="server"></asp:TextBox></div>
<div>
<asp:Label ID="Answer" runat="server" Text="找回密碼答案："></asp:Label>
<asp:TextBox ID="TextBox4" runat="server"></asp:TextBox></div>
<div >
<asp:Label ID="Email" runat="server" Text="電子郵件："></asp:Label>
<asp:TextBox ID="TextBox5" runat="server"></asp:TextBox></div>
<div >
<asp:Label ID="Label1" runat="server" Text="驗證碼："></asp:Label>
<asp:TextBox ID="CheckCode" runat="server" Width="85px"></asp:TextBox>
<asp:Image id="Image1" runat="server" ImageUrl="Validate.aspx"></asp:Image></div>
<div>
<asp:Button ID="Button1" runat="server" Text="確定" OnClick="Button1_Click" /></div>
<div class="text">
<asp:Label ID="Message" runat="server" ></asp:Label></div>
</div>
</form>
</body>
</html>
-------------------------register.aspx.cs-------------------
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;
namespace MyRegister
{
public partial class Register : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void Button1_Click(object sender, EventArgs e)
{
string checkcode = CheckCode.Text;
//Response.Write(Session["VNum"]);
if (checkcode == Session["VNum"].ToString() || Session["VNum"].ToString()==null)//注意Session["VNum"].ToString()，必須加上ToString()，因//爲Session["VNum"]是對象。
Response.Redirect ("default.aspx");
else
Message.Text = "驗證碼錯誤或爲空！";
}
}
}
---------------------------------
其中註釋的地方應特別注意