asp.net扩展login控件时，图片验证码的问题，
对login控件进行扩展，加入图片验证码，第一次运行是正确的，然后进入系统后 点注销，系统返回到login页面，这时图片显示不出来，只显示了alt的文字，各位有没有遇到过这问题，
其中验证码生成文件imageValidate.cs 中主要代码
public partial class imageValidate : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
//生成4位的验证码
/*string tmp = RndNum(4);
HttpCookie cookie = new HttpCookie( "ImageV ", tmp);
//Response.Cookies[ "ImageV "].Value=tmp;
Response.Cookies.Add(cookie);
this.ValidateCode(tmp);*/
CreateCheckCodeImage(GenerateCheckCode());
}
private string GenerateCheckCode()
{
int number;
char code;
string checkCode = String.Empty;
System.Random random = new Random();
for (int i = 0; i < 5; i++)
{
number = random.Next();
if (number % 2 == 0)
code = (char)( '0 ' + (char)(number % 10));
else
code = (char)( 'A ' + (char)(number % 26));
checkCode += code.ToString();
}
Response.Cookies.Add(new HttpCookie( "CheckCode ", checkCode));
return checkCode;
}
private void CreateCheckCodeImage(string checkCode)
{
if (checkCode == null || checkCode.Trim() == String.Empty)
return;
System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 22);
Graphics g = Graphics.FromImage(image);
try
{
//生成随机生成器
Random random = new Random();
//清空图片背景色
g.Clear(Color.White);
//画图片的背景噪音线
for (int 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.FontStyle.Italic));
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);
//画图片的前景噪音点
for (int i = 0; i < 100; i++)
{
int x = random.Next(image.Width);
int y = random.Next(image.Height);
image.SetPixel(x, y, Color.FromArgb(random.Next()));
}
//画图片的边框线
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);
Response.ClearContent();
Response.ContentType = "image/Gif ";
Response.BinaryWrite(ms.ToArray());
}
finally
{
g.Dispose();
image.Dispose();
}
}
}
在login控件中加入：
<tr>
<td style= "width: 151px ">
<asp:Label ID= "Label1 " runat= "server " AssociatedControlID= "Password "> 验证码: </asp:Label>
</td>
</tr>
<tr>
<td style= "width: 151px ">
<asp:TextBox ID= "txtImgValid " runat= "server " Font-Size= "0.8em " > </asp:TextBox>
<img id= "imgValid " alt= "单击可刷新 " src= "imageValidate.aspx " />
</td>
<td>
</tr>
login.cs中对应的代码为
protected void Login1_Authenticate(object sender, AuthenticateEventArgs e)
{
TextBox txtImage = Login1.FindControl( "txtImgValid ") as TextBox;
if (Request.Cookies[ "CheckCode "] == null)
{
Response.Write( " <script language= 'javascript '> alert( '您应启动cookies! ') </script> ");
e.Authenticated = false;
return;
}
if (String.Compare(Request.Cookies[ "CheckCode "].Value, txtImage.Text, true) != 0)
{
Response.Write( " <script language= 'javascript '> alert( '不匹配! ') </script> ");
e.Authenticated = false;
return;
}
e.Authenticated = true;
}
[解决办法]
用Session
[解决办法]
登录成功后，顺手把Session清掉
[解决办法]
你用的是Cookies且你的页面加载时也没有判断，注意Page.IsPageBack的用法
[解决办法]
如果是这样的话，那你把IE设置中的， "检查所存网页的较新版本 "设置为 "每次访问此页时检查 "试试
