经常在论坛里看到有问怎么实现验证码的帖子,其实关于验证码的文章在CSDN,DEV-CLUB等网站上都有很多,但是很多文章只讲诉了如何输出一个随机生成数字或字符的图象,当然了,这个是验证码的核心了,但是对很多ASP.NET的初学者来说,怎么使用它生成的图象又成了一个问题(论坛有不少问这个的),这也是我写本文的一个原因.
言归正传,关于验证码的原理,我就不多说了,大家可以参见其他文章,文末附有完整的实例代码,里面有详细的注释,你可以跳过解说文字,直接使用
首先,我要简要说说Session和ViewState的用法,因为后面会用到它
把数据存储在Session中:Session("key")="test"
从Session取值:dim testvalue as string=Session("key")
类似的:
把数据存储在ViewState中:ViewState("key")="test"
从ViewState中取值:dim testvalue as string=ViewState("key")
关于ViewState的更详细的资料,你可以参看MSDN的<<ASP.NET ViewState 初探>>一文
百闻不如一见,有时代码本身就比任何解说更有表现力,所以在此就不对代码解说太多了,本文实现的验证码需要用到两个文件:
gif.aspx 该文件用于生成验证码
ValidateCode.aspx 该文件用来测试验证码(即如何使用)
下面给出gif.aspx的完整代码:
<%@ import namespace="System"%>
<%@ import namespace="System.io"%>
<%@ import namespace="System.Drawing"%>
<%@ import namespace="System.Drawing.Imaging"%>
<script language="vb" runat="server">
Sub Page_Load(Sender as object,e as eventargs)
'RndNum是一个自定义函数
dim VNum as string=RndNum(4)
Session("VNum")=VNum
ValidateCode(VNum)
End Sub
'生成图象验证码函数
Sub ValidateCode(VNum)
Dim Img as System.Drawing.Bitmap
Dim g as Graphics
Dim ms as MemoryStream
dim gheight as integer=Int(Len(VNum)*11.5)
'gheight为图片宽度,根据字符长度自动更改图片宽度
img=new BitMap(Gheight,20)
g=Graphics.FromImage(img)
g.DrawString(VNum,(New Font("Arial",10)),(New SolidBrush(color.blue)),3,3)'在矩形内绘制字串(字串,字体,画笔颜色,左上x.左上y)
ms=New MemoryStream()
img.Save(ms,ImageFormat.Png)
Response.ClearContent() '需要输出图象信息 要修改HTTP头
Response.ContentType="image/Png"
Response.BinaryWrite(ms.ToArray())
g.Dispose()
img.Dispose()
Response.End()
End Sub
'--------------------------------------------
'函数名称:RndNum
'函数参数:VcodeNum--设定返回随机字符串的位数
'函数功能:产生数字和字符混合的随机字符串
Function RndNum(VcodeNum)
dim Vchar as string="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,W,X,Y,Z"
dim VcArray() as string=split(Vchar,",") '将字符串生成数组
dim VNum as string=""
dim i as byte
For i=1 to VcodeNum
Randomize
VNum=VNum & VcArray(Int(35*Rnd)) '数组一般从0开始读取,所以这里为35*Rnd
Next
Return VNum
End Function
</script>
那么又应该如何使用该文件生成的图象验证码,看这句代码:
<asp:Image id="Image1" runat="server" ImageUrl="gif.aspx" />
这就是用来显示验证码的Image控件,你可以把它放在任何你喜欢的地方,下面的给出详细的使用代码,你把它保存为ValidateCode.aspx,并把它和gif.aspx放在同一目录下,在浏览器中打开ValidateCode.aspx,就可以测试它的效果了:
<script language="vb" Runat="Server">
Sub Page_Load(Sender as object,e as eventargs)
dim VNum as string=Session("VNum")
Session.Abandon()
ViewState("VNum")=VNum
End Sub
'下面的事件代码是用来测试验证码,可以根据需要更改
Sub btnSubmit_click(sender as object,e as eventargs)
'判断输入的验证码与所给是否相同
If txtValidateCode.text=Cstr(ViewState("VNum")) then
lblShow.text="<font color='red'>提示:验证通过</font>"
Else
lblShow.text="所填写的验证码与所给的不符"
End If
End Sub
</script>
<html>
<body>
<form runat="server">
<div align="center">
<table width="750">
<!--DWLayoutTable-->
<tr>
<td width="256" height="46"> </td>
<td width="9"> </td>
<td width="88"> </td>
<td width="87"> </td>
<td width="100"> </td>
<td width="68"> </td>
<td width="97"> </td>
</tr>
<tr>
<td height="21"></td>
<td></td>
<td colspan="3" valign="top"><asp:label ID="lblShow" runat="server"></asp:label></td>
<td> </td>
<td> </td>
</tr>
<tr>
<td height="14"></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
<tr>
<td height="21"> </td>
<td colspan="2" valign="middle">验证码:</td>
<td valign="top"><asp:Image id="Image1" runat="server" ImageUrl="gif.aspx" /></td>
<td> </td>
<td> </td>
<td> </td>
</tr>
<tr>
<td height="20"> </td>
<td colspan="2" valign="top">输入验证码:</td>
<td valign="top"><asp:textbox ID="txtValidateCode" runat="server" TextMode="SingleLine" /></td>
<td colspan="2" valign="middle"><font color="#FF0000" size="2">*注意:区分大小写</font></td>
<td> </td>
</tr>
<tr>
<td height="25"> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
</tr>
<tr>
<td height="19"> </td>
<td> </td>
<td> </td>
<td valign="top"><asp:button ID="btnSubmit" runat="server" Text="比较" onclick="btnSubmit_click" /></td>
<td> </td>
<td> </td>
<td> </td>
</tr>
</table>
</div>
</form>
</body>
</html>
对该文的评论
cwbboy ( 2004-02-09)
///
/// 将校验码生成图片
///
/// 校验码字符串
private void ValidateCode(string VNum)
{
int Gheight=(int)(VNum.Length * 11.5);
//gheight为图片宽度,根据字符长度自动更改图片宽度
System.Drawing.Bitmap Img = new System.Drawing.Bitmap(Gheight,20);
Graphics g = Graphics.FromImage(Img);
g.DrawString(VNum,new System.Drawing.Font("Arial",10),new System.Drawing.SolidBrush(Color.Red),3,3); //在矩形内绘制字串(字串,字体,画笔颜色,左上x.左上y)
System.IO.MemoryStream ms=new System.IO.MemoryStream();
Img.Save(ms,System.Drawing.Imaging.ImageFormat.Png);
Response.ClearContent(); //需要输出图象信息 要修改HTTP头
Response.ContentType="image/Png";
Response.BinaryWrite(ms.ToArray());
g.Dispose();
Img.Dispose();
Response.End();
}
///
/// 生成验证码
///
/// 校验码长度
/// 返回校验码
private string GenerateCheckCode(int CodeLength)
{
string Vchar="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,W,X,Y,Z";
string[]VcArray=Vchar.Split(new char[]{','}); //将字符串生成数组
string VNum ="";
for(byte i=1;i<=CodeLength;i++)
{
Random ro=new Random();
VNum+=VcArray[(int)(35*ro.NextDouble())]; //数组一般从0开始读取,所以这里为35*Rnd
}
return VNum;
}
我应用过的一个例子,供楼主参考:
ValidateCode 随机产生验证码
------------------------------------------
ValidateCode.aspx
Imports System
Imports System.Drawing
Imports System.Drawing.Imaging
Imports System.IO
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim My_Stream As MemoryStream = Get_Images(20, 5, "#E0E0E0") '参数分别为:字体大小,验证码位数,背景色
Show_image(My_Stream) '显示内存图像
My_Stream.Close() '关闭打开的流文件
End Sub
'将字符转换成图像
'参数说明:
' Font_Size 字体大小
' Char_Number 验证码位数
' BackgroundColor 背景色
Function Get_Images(ByVal Font_Size As Integer, ByVal Char_Number As Integer, ByVal BackgroundColor As String) As MemoryStream
Dim image_w As Integer = Int(Font_Size * 1.5) + Font_Size * Char_Number
Dim image_h As Integer = Int(Font_Size / 2)
'******************************************
' 保存图像的 宽度 和 高度,供调用页面使用
'******************************************
Session("image_w") = image_w
Session("image_h") = image_h
Dim Temp_Bitmap As Bitmap '封装GDI+位图
Dim Temp_Graphics As Graphics '封装GDI+绘图面
Dim Color_Back As Color = ColorTranslator.FromHtml(BackgroundColor) '背景颜色
Temp_Bitmap = New Bitmap(image_w, 5 * image_h, PixelFormat.Format32bppRgb) '确定背景大小
Temp_Graphics = Graphics.FromImage(Temp_Bitmap)
Temp_Graphics.FillRectangle(New SolidBrush(Color_Back), New Rectangle(0, 0, image_w, 5 * image_h)) '绘制背景
Dim Sesson_Company As String = "" '为了进行验证比较
Dim n As Integer
For n = 0 To Char_Number - 1
Dim Show_Str As String = getChar() '要显示为图像的字符
Sesson_Company = Sesson_Company & Show_Str
Dim Show_Str_Font_Size As Integer = Int(3 * Rnd() + (Font_Size - 2)) '字体随机大小
Dim Color_Font As Color = ColorTranslator.FromHtml(getColor()) '字体随机颜色
Dim Show_Font_Name As String = getFont() '字体
Dim Show_Str_Font As Font = New Font(Show_Font_Name, Show_Str_Font_Size, FontStyle.Bold) '定义文本格式(字体,字号,粗体)
Temp_Graphics.DrawString(Show_Str, Show_Str_Font, New SolidBrush(Color_Font), Int(Font_Size / 2) + n * Font_Size, Int(image_h * 0.125 * Rnd() + image_h * 0.08)) '绘出字符 '绘字符的Y方向下波动+4
Next
'********************************
' 保存到session便于调用的页面比较
'********************************
Session("imagenumber") = Trim(Sesson_Company)
Font_Size = Font_Size * 4
image_h = Int(2.5 * Font_Size)
Dim Temp_Stream As MemoryStream = New MemoryStream
Temp_Bitmap.Save(Temp_Stream, ImageFormat.Jpeg)
Temp_Graphics.Dispose() '释放资源
Temp_Bitmap.Dispose() '释放资源
Temp_Stream.Close() '关闭打开的流文件
Return Temp_Stream '返回流
End Function
'显示内存图像
Function Show_image(ByVal Show_Stream As MemoryStream)
Response.ClearContent()
Response.ContentType = "Image/Jpeg"
Response.BinaryWrite(Show_Stream.ToArray())
Response.End()
End Function
'获得随机字符 0-9 a-z A-Z
Function getChar() As String
Dim Char_array(5)
Char_array(0) = Chr(Int(10 * Rnd() + 48))
Char_array(1) = Chr(Int(26 * Rnd() + 65))
Char_array(2) = Chr(Int(26 * Rnd() + 65))
Char_array(3) = Chr(Int(26 * Rnd() + 97))
Char_array(4) = Chr(Int(26 * Rnd() + 97))
Return Char_array(Int(5 * Rnd()))
End Function
'获得随机颜色
Function getColor() As String
Dim int_a As Integer
Dim int_b As Integer
Dim int_c As Integer
int_a = Int(180 * Rnd() + 20)
int_b = Int(180 * Rnd() + 20)
int_c = Int(180 * Rnd() + 20)
If int_a > 150 And int_b > 150 And int_c > 150 Then int_a = Int(150 * Rnd() + 20)
Return "#" & Hex(int_a) & Hex(int_b) & Hex(int_c)
End Function
'获得随机字体
Function getFont() As String
Dim font_array(7)
font_array(0) = "Arial Black"
font_array(1) = "BatangChe"
font_array(2) = "Century"
font_array(3) = "Arial Black"
font_array(4) = "Arial Black"
font_array(5) = "Arial Black"
font_array(6) = "Arial Black"
Return font_array(Int(7 * Rnd()))
End Function
------------------------------------------
应用方法:
<asp:Image id="Image1" style="Z-INDEX: 108; LEFT: 32px; POSITION: absolute; TOP: 80px" runat="server"
ImageUrl="ValidateCode.aspx" Width='<%# Session("image_w")%>' Height='<%# Session("image_h") %>'>
</asp:Image>
------------------------------------------
提取真正的值:
例如:
Label1.Text = Session("imagenumber")
注意:
Session("imagenumber") 中的 值 提取通常比页面显示的慢一个“刷新次” ;
参照别人的一个:
ASP.Net实现验证码
-----------------------------------start----------------------------------------------
using System.Drawing;
using System.Drawing.Imaging;
private void Page_Load(object sender, System.EventArgs e)
{
// 在此处放置用户代码以初始化页面
//RndNum是一个自定义函数
string VNum=RndNum(4); //这里的数字4代表显示的是4位的验证字符串!
Session["VNum"]=VNum;
ValidateCode(VNum);
}
//生成图像函数
private void ValidateCode(string VNum)
{
int Gheight=(int)(VNum.Length * 11.5);
//gheight为图片宽度,根据字符长度自动更改图片宽度
System.Drawing.Bitmap Img = new System.Drawing.Bitmap(Gheight,20);
Graphics g = Graphics.FromImage(Img);
g.DrawString(VNum,new System.Drawing.Font("Arial",10),new System.Drawing.SolidBrush(Color.Red),3,3);
//在矩形内绘制字串(字串,字体,画笔颜色,左上x.左上y)
System.IO.MemoryStream ms=new System.IO.MemoryStream();
Img.Save(ms,System.Drawing.Imaging.ImageFormat.Png);
Response.ClearContent(); //需要输出图象信息 要修改HTTP头
Response.ContentType="image/Png";
Response.BinaryWrite(ms.ToArray());
g.Dispose();
Img.Dispose();
Response.End();
}
//生成随机数函数中从Vchar数组中随机抽取
//字母区分大小写
public string RndNum(int VcodeNum)
{
string Vchar = "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,W,X,Y,Z" ;
string[] VcArray = Vchar.Split(',') ;
string VNum = "" ;//由于字符串很短,就不用StringBuilder了
int temp = -1 ;//记录上次随机数值,尽量避免生产几个一样的随机数
//采用一个简单的算法以保证生成随机数的不同
Random rand =new Random();
for ( int i = 1 ; i < VcodeNum+1 ; i++ )
{
if ( temp != -1)
{
rand =new Random(i*temp*unchecked((int)DateTime.Now.Ticks));
}
//int t = rand.Next(35) ;
int t=rand.Next(35);
if (temp != -1 && temp == t)
{
return RndNum( VcodeNum );
}
temp = t ;
VNum += VcArray[t];
}
return VNum ;
}
-----------------------------------end--------------------------------------------
下面是Login.Aspx在在调用提交按钮的响应事件中
public void doit(object sender, System.EventArgs e)
{
if(Page.IsValid)
{
string VNum;
VNum=Session["VNum"].ToString();
ViewState["VNum"]=VNum;
if(this.Vcode.Text==ViewState["VNum"].ToString())
{
Hover.Manage.CheckLogin obj=new Hover.Manage.CheckLogin();
string name=username.Text;
string password=FormsAuthentication.HashPasswordForStoringInConfigFile(pass.Text.ToString(),"md5");
if(!obj.checklogin(name,password))
{
Response.Redirect("../Error.aspx?action=Errorlogin");
Response.End();
return;
}
else
{
Session.Add("adminname",name);
Session.Add("adminpass",password);
Response.Redirect("Default.aspx");
Response.End();
return;
}
}
else
{
Response.Write("<script>alert(\"请输入正确的附加码!\");</script>");
}
}
}
如果提交过来的验证字符串正确就验证是否是合法用户!
否则弹出提示返回登陆页!你也可以简化此页!
if(this.Vcode.Text==ViewState["VNum"].ToString())
{
Response.Write("验证码正确");
}
else
{
Response.Write("验证码错误!");
}