Login控件也可添加图文验证码_[Asp.Net教程]

对asp.net提供的Login控件进行扩展，在密码后面加一图文验证功能以防止自动注册程序。
1.添加imageValidate.aspx，在头部添加信息
<% Response.Buffer = true ;%>
<% Response.ExpiresAbsolute = DateTime.Now.AddSeconds(-1);%>
<% Response.Expires = 0 ;%>
<% Response.CacheControl = "no-cache" ; %>
在imageValidate.aspx.cs中的代码如下：
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();
}
Session["CheckCode"] = checkCode;


//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();
}
}
这就是生成验证码的页面
2.将这页面添加到login控件中：
拖曳一Login控件，将之切换到模式下，在Html源文件中在表格中密码那行后添加：






验证码:





















其中ImageUrl="~/public/imageValidate.aspx“ 的imageValidate.aspx指的就是我们第一步建立的文件。
3.在login控件的authenticate事件中加入代码
protected void Login1_Authenticate(object sender, AuthenticateEventArgs e)
{
TextBox txtImage = Login1.FindControl("txtImgValid") as TextBox;


if (Session["CheckCode"] == null)
{
Response.Write("");
e.Authenticated = false;
return;
}

if (String.Compare(Session["CheckCode"] .ToString(),txtImage.Text,true)!=0)
{
Response.Write("");
e.Authenticated = false;
return;
}

e.Authenticated = true;


}

单击登录按钮后顺便将session清空
protected void LoginButton_Click(object sender, EventArgs e)
{
Session["CheckCode"] = null;
}
运行结果如图：


来源：网络