你在点击图片以后，指定的页面还是原来的页面，当然看不到任何改变了！
你可以在页面的PageLoad事件里面改变页面图片上的文字！或者在图片的onclick事件中，指定另外一个页面才会有改变呀，
如果只是想实现验证码的功能的话，最好将做一个验证码的WEB控件。
参考以下代码：
using System;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.ComponentModel;
using System.IO;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
namespace WebValidateCode
{
public enum GraphicType
{
Jpg = 0,
Gif = 1,
Png = 2,
Bmp = 3,
}
//[ToolboxBitmap(@"D:\DotnetApp\ValidateCode\ValidateCode.bmp") ] //设置控件在工具箱上的图标
public class ValidateCode : System.Web.UI.WebControls.WebControl ,INamingContainer
{
private int pCodelen=5;
private int pChartWidth=100;
private int pChartHeight=20;
private GraphicType pChartType;
private string pAuthenCode;
private string pTempImageURLPath="/temp";
private string pAuthenImageFullname;
private string pAuthenImageFullURL;
//生成校验码的变量 start
private Bitmap validateImage;
private Graphics g;
//生成校验码的变量 End
private TextBox txt=new TextBox();
private System.Web.UI.WebControls.Image img= new System.Web.UI.WebControls.Image();
#region 定义控件事件
public delegate void GraphicCreated(object sender, EventArgs e);
public event EventHandler GraphicOK; //在校验图片生成结束以后触发
protected virtual void OnGraphicOK(object sender, EventArgs e)
{
if (GraphicOK != null)
{
//Invokes the delegates.
GraphicOK(sender, e);
}
}
#endregion
#region 控件属性
//生成校验码的长度
[Bindable(true),Browsable(true),Category("Appearance"),DefaultValue(true),Description("需要验证码的长度,建议在5~8位之间!")]
public int CodeLength
{
get
{
return pCodelen;
}
set
{
pCodelen = value;
}
}
//生成校验码的长度
[Bindable(true),Browsable(true),Category("Appearance"),DefaultValue(true),Description("生成验证码图片的临时存放路径,要求必须是网站下的虚拟目录!")]
public string TempImageURLPath
{
get
{
return pTempImageURLPath;
}
set
{
pTempImageURLPath = value;
}
}
[Bindable(true),Browsable(true),Category("Appearance"),DefaultValue(GraphicType.Jpg), Description("选择生成校验图文件的类型(Jpg;Gif;Png;Bmp)!")]
public GraphicType ChartType
{
get
{
return pChartType;
}
set
{
pChartType = value;
}
}
//生成校验码图片的宽度
public int ChartWidth
{
get
{
return pChartWidth;
}
set
{
pChartWidth = value;
}
}
//生成校验码图片的高度
public int ChartHeight
{
get
{
return pChartHeight;
}
set
{
pChartHeight = value;
}
}
//需要生成的校验码
public string AuthenCode
{
get
{
return pAuthenCode;
}
set
{
pAuthenCode = value;
}
}
#endregion
/// <summary>
/// 将此控件呈现给指定的输出参数。
/// </summary>
/// <param name="output"> 要写出到的 HTML 编写器 </param>
protected override void Render(HtmlTextWriter output)
{
System.Web.UI.WebControls.Image objImage;
//TextBox objTxt;
//绘制包含的控件
objImage = (System.Web.UI.WebControls.Image) Controls[0];
//objTxt = (TextBox) Controls[1];
if(pAuthenCode==null)
pAuthenCode=GetValidateCode();
OnGraphicOK(this,EventArgs.Empty );
GetRandomImage(pAuthenCode);
objImage.ImageUrl=pAuthenImageFullURL;
objImage.RenderControl(output);
}
/// <summary>
/// 给控件添加子控件
/// </summary>
protected override void CreateChildControls( )
{
//Controls.Add(btn);
Controls.Add(img);
//Controls.Add(txt);
}
/// <summary>
/// 控件Load时候属性的初始化
/// </summary>
/// <param name="e"></param>
protected override void OnLoad(System.EventArgs e)
{
EraseOldGraphic(); //删除过期的图片
}
/// <summary>
/// 生成随机的
/// </summary>
private void MakeRandomFileName()
{
string strRandName=DateTime.Now.Ticks.ToString()+".jpg";
pAuthenImageFullname=this.Page.MapPath(TempImageURLPath)+@"\"+strRandName;
pAuthenImageFullURL=TempImageURLPath+"/"+strRandName;
}
private void GetRandomImage(string strValidateCode)
{
//生成随即图片的全名,和全URL
MakeRandomFileName();
validateImage = new Bitmap(pChartWidth, pChartHeight, PixelFormat.Format24bppRgb); // .Format24bppRgb);
g = Graphics.FromImage(validateImage);
g.Clear(Color.LightGray) ;
//g.DrawString(strValidateCode , new Font("宋体",16,FontStyle.Bold),new SolidBrush(Color.DarkRed),new PointF(2,2));
for(int i=0;i<strValidateCode.Length;i++)
{
Random r = new Random();
PointF startPos=new PointF(r.Next(3,6)+(r.Next(12,14)*i ),r.Next(-1,2) );
g.DrawString(strValidateCode.Substring(i,1) , new Font("宋体",14,FontStyle.Italic),new SolidBrush(Color.Blue),startPos);
}
//g.FillRectangle(new LinearGradientBrush(new Point(0,0), new Point(120,30), Color.FromArgb(0,0,0,0),Color.FromArgb(255,255,255,255)),0,0,120,30);
switch(pChartType)
{
case GraphicType.Jpg:
validateImage.Save(pAuthenImageFullname, ImageFormat.Jpeg);
break;
case GraphicType.Gif:
validateImage.Save(pAuthenImageFullname, ImageFormat.Gif);
break;
case GraphicType.Png:
validateImage.Save(pAuthenImageFullname, ImageFormat.Png);
break;
case GraphicType.Bmp:
validateImage.Save(pAuthenImageFullname, ImageFormat.Bmp);
break;
default:
validateImage.Save(pAuthenImageFullname, ImageFormat.Jpeg);
break;
}
validateImage.Dispose();
g.Dispose();
}
/// <summary>
/// 动态从数字和字母组成的元素中动态选择生成校验码
/// </summary>
private string GetValidateCode()
