实现验证码局部刷新

CS代码：

using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
using System.Drawing.Drawing2D;

namespace ValidateTest
{
/// <summary>
/// WebForm3 的摘要说明。
/// </summary>
public class WebForm3 : System.Web.UI.Page
{
public const String auSubject="shawl.qiu c# .net checkcode class";
public const String auVersion="v1.0";
public const String au="shawl.qiu";
public const String auEmail="";
public const String auBlog="";
public const String auCreateDate="2007-2-1";

private void Page_Load(object sender, System.EventArgs e)
{
String sRndStr=WebForm3.rndStr(4);
WebForm3.general(sRndStr);
}

#region Web 窗体设计器生成的代码
override protected void OnInit(EventArgs e)
{
//
// CODEGEN: 该调用是 ASP.NET Web 窗体设计器所必需的。
//
InitializeComponent();
base.OnInit(e);
}

/// <summary>
/// 设计器支持所需的方法 - 不要使用代码编辑器修改
/// 此方法的内容。
/// </summary>
private void InitializeComponent()
{
this.Load += new System.EventHandler(this.Page_Load);

}
#endregion

public static void general(String sCc)
{
Int32 ccLen=sCc.Length;

String ccFtFm="Arial";
Int32 ccFtSz=12;

Int32 ccWidth=ccLen*ccFtSz+1;
Int32 ccHeight=ccFtSz+5;

using(Bitmap oImg = new Bitmap(ccWidth, ccHeight))
{
using(Graphics oGpc=Graphics.FromImage(oImg))
{
HatchBrush hBrush = new HatchBrush(HatchStyle.DashedVertical,
Color.Yellow, Color.Silver);
oGpc.FillRectangle(hBrush, 0, 0, ccWidth, ccWidth);

oGpc.DrawString(sCc,new System.Drawing.Font(ccFtFm,ccFtSz, FontStyle.Bold),
new System.Drawing.SolidBrush(Color.Black),0,0);

//-----------------------边框
Pen blackPen = new Pen(Color.Black, 1);
oGpc.DrawLine(blackPen, 0, ccHeight, 0, 0); // 左竖线
oGpc.DrawLine(blackPen, 0,0,ccWidth,0); // 顶横线
oGpc.DrawLine(blackPen, ccWidth-1,0,ccWidth-1,20); // 右竖线
oGpc.DrawLine(blackPen, 0, ccHeight-1, ccWidth, ccHeight-1); // 底横线

writeImg(oImg);
}
}
} // end public static void general

public static String rndStr(Int32 len)
{
String sTemp="";
String sForRnd="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,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[] aRnd=sForRnd.Split(',');

Random oRnd=new Random();
Int32 iArLen=aRnd.Length;

for(Int32 i=0; i<len; i++)
{
sTemp+=aRnd[oRnd.Next(0,iArLen)];
}
return sTemp;
} // end public static String rndStr
//-----------------------------------end public static method

//-----------------------------------begin private static method
private static void writeImg(Bitmap oImg)
{
using(System.IO.MemoryStream ms=new System.IO.MemoryStream())
{
oImg.Save(ms,System.Drawing.Imaging.ImageFormat.Png);
HttpContext.Current.Response.ClearContent();
HttpContext.Current.Response.ContentType="image/Png";
HttpContext.Current.Response.BinaryWrite(ms.ToArray());
}
} // end private static void writeImg
}

}

HTML代码：

在其他页面

<script language="javascript">

function update()

{

var n=Math.random();

document.getElementById("a1").src="WebForm3.aspx?r="+n;

}

<script>

<img src="WebForm3.aspx" id="a1">

<a href="javascript:update()">看不清楚，换一张图片</a>
function update()
{
var n = Math.random() ;
document.getElementById("a1").src="WebForm3.aspx?r=" + n ;
//document.getElementById("a1").src="WebForm5.aspx";
}

function update()
{
var n = Math.random() ;
document.getElementById("a1").src="WebForm3.aspx?r=" + n ;
//document.getElementById("a1").src="WebForm5.aspx";
}

function update()
{
var n = Math.random() ;
document.getElementById("a1").src="WebForm3.aspx?r=" + n ;
//document.getElementById("a1").src="WebForm5.aspx";
}