asp.net之生成验证码的方法集锦(一)

现在很多网站都有注册登录的页面,为了更好的满足用户体验和网站的安全性,很多网站都采用动态生成的图形码或者是附加码进行验证,下面把生成验证码的方法给大家整理如下.

实现验证技术就是在服务器端生成一个随机数,并将其保存在内存中,发送给浏览器,并以图片的形式提交给用户。之前在做项目过程中,完成了一个利用script进行用户注册及登录的验证码时,发现有各种生成验证码的方式,下面主要是几种不同的生成验证码的方式:

1、绘制纯数字的网站验证码

本实例实现的是数字验证码技术,即随机生成4位数字作为验证码。在开发绘制会员登录验证模块时可以使用数字验证码技术。

■设计过程

在一个新建的窗体CheckCode.aspx中编写生成数字验证码的方法:

private string RndNum()
 {
 int number;
 char code;
 string checkCode = String.Empty;
 System.Random random = new Random();
 for (int i = 0; i < 4; 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("yzmcode", 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();
 }
 } 

然后在Page_Load中调用CreateCheckCodeImage():
 

protected void Page_Load(object sender, EventArgs e)
 {
 this.CreateCheckCodeImage(RndNum()); 
}
那么在我们登录的窗口中就可以通过简单的控件:
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
 <asp:ImageButton ID="ImageButton2" runat="server" ImageUrl="~/CheckCode.aspx" Width="50" Height="30"/><asp:Label
 ID="Label1" runat="server" Text="看不清楚?点击图片换一个" Height="16px" 
 Font-Size="Small" ForeColor="Red"></asp:Label>
 <br />
 <asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Button" />
在Button1_Click中对验证码输入的正确性进行判断:
protected void Button1_Click(object sender, EventArgs e)
{
 if (String.Compare(Request.Cookies["yzmcode"].Value, TextBox1.Text, true) != 0)
 {
 Response.Write("<script>alert('验证码错误!')</script>");
 }
 else
 Response.Write("<script>alert('验证码正确!')</script>");
}

2、绘制数字与字母组合的网站验证码

和纯数字的很相似,具体区别在随机生成字符串的方法中

 

private string GenerateCheckCode()
 {
 int number;
 char code;
 string checkCode = String.Empty;
 Random random = new Random();
 for (int i = 0; i < 4; 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;
 }

字符串生成后,接下来就是将该字符串绘制成图片显示出来。代码如下:

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 < 2; 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.Black), x1, y1, x2, y2);
 }
 Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold));
 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();
 }
 } 

在登录的窗口进行验证码输入是否正确的判断:

protected void Button1_Click(object sender, EventArgs e)
 {
 HttpCookie cookie = Request.Cookies["CheckCode"];
 if (cookie.Value == this.TextBox1.Text.Trim())
 {
 Response.Write("<script>alert('验证码正确!')</script>");
 }
 else
 {
 Response.Write("<script>alert('验证码错误!')</script>"); 
 }
 }

那么有关于数字与字母组合的网站验证码就生成了。

3、四则运算式的验证码

其他的和数字和字母混合生成的验证码相似,我就不写了,具体区别在随机生成四则运算式的方法中,如下:

 

private string GenerateCheckCode()
 {
 Random rd = new Random();
 int Results = 0;
 int Num1 = rd.Next(10);
 int Num2 = rd.Next(10);
 string Expressions = "";
 int F = (rd.Next(4) + 1);
 switch (F)
 {
 case 1:
 Results = Num1 + Num2;
 Expressions = Num1 + "+" + Num2;
 break;
 case 2:
 Results = Num1 - Num2;
 Expressions = Num1 + "-" + Num2;
 break;
 case 3:
 Results = Num1 * Num2;
 Expressions = Num1 + "*" + Num2;
 break;
 case 4:
 if (Num2 > 0)
 {
 Results = Convert.ToInt16(Num1 / Num2);
 Expressions = Num1 + "/" + Num2;
 }
 else
 {
 Results = Num1;
 Expressions = Num1 + "/1";
 }
 break;
 }
 Session["Code"] = Results.ToString();
 return Expressions;
}

此篇文章主要介绍了三种方法生成验证码,希望大家喜欢。

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