ASP.NET中登录页验证码的实现 分类： ASP.NET 2012-03-08 22:44 4936人阅读 评论(5) 收藏

在做一个登录页时，我们通常需要设置验证码，防止非法人员通过其他手段非法登录。在做一个页面的验证码时，我们需要先建立一个Active的Web页面，来随机的产生数字和字母，同时把产生的数字存储在Session中，传递给登录页，用来验证。并且定义一个画板，在Active页面绘出验证码的背景颜色，在Active页面的代码如下：

protected void Page_Load(object sender, EventArgs e)
{
//显示验证码
this.GenImg(this.GenCode(4));
Session["image"] = this.GenCode(4);
Server.Transfer("Default.aspx");
//Console.WriteLine(this.GenCode(4));
}
private string GenCode(int num)
{
string [] source={"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"};
string code = "";
//创建Random类的实例
Random rd = new Random();
//获取验证码
for (int i = 0; i < num; i++)
{
code += source[rd.Next(0, source.Length)];

}
//返回产生的验证码
return code;
}

//生成图片
private void GenImg(string code)
{
//定义一个画板
Bitmap myPalette = new Bitmap(60, 20);
//在画板上定义绘图的实例
Graphics gh = Graphics.FromImage(myPalette);
//定义一个矩形
Rectangle rc = new Rectangle(0, 0, 60, 20);
//填充矩形
gh.FillRectangle(new SolidBrush(Color.Blue), rc);
//在矩形内画出字符串
gh.DrawString(code, new Font("宋体", 16), new SolidBrush(Color.White), rc);
//将图片显示出来
myPalette.Save(Response.OutputStream, ImageFormat.Jpeg);
gh.Dispose();
myPalette.Dispose();
}

当我们完成了，在Active页面动态的随机产生验证码以后，我们要在登录页接收，随机产生的验证码，并显示出来，代码如下：

protected void Page_Load(object sender, EventArgs e)
{
//设置btnimage控件的ImageUrl属性为验证码的页面
this.ImageButton1.ImageUrl = "Active.aspx";
}
protected void Button1_Click(object sender, EventArgs e)
{
string Code =Session["image"].ToString().Trim();
//Console.WriteLine(Code);

string Txtbox = this.TextBox3.Text.ToString().Trim();
if (Code==Txtbox.ToUpper())
{
Response.Redirect("Result.aspx");
}
else
Response.Write("<script language='javascript'>alert('跳转失败！');</script>");
}

到此，就完成了一个动态产生验证码的全过程，并且完成验证的代码。