ASP.NET 验证码示例
<%@ Page Language="C#" %>
<%@ Import Namespace="System.Drawing" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<!--
1.准备Bitmap对象 image:
System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 20);
2.利用Graphics对象g在上面画图:
Graphics g = Graphics.FromImage(image);
g.DrawString(checkCode, f, b, 3, 3);
3.然后Response.BinaryWrite输出:
Response.BinaryWrite(ms.ToArray());
优化想法：
将验证码以js脚本可读取的方式发送到客户端；
客户端先出发js脚本的验证，通过后才允许提交；
提供重新获取验证码功能。
-->
<script runat="server">
/// <summary>
/// 输入要求的验证码的位数，返回一个验证码字符串
/// </summary>
/// <param name="codeCount">验证码的位数</param>
/// <returns>验证码字符串</returns>
private string CreateRandomCode(int codeCount)
{
string allChar = "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," +
"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[] allCharArray = allChar.Split(',');
int allCharLen = allCharArray.Length;
string randomCode = "";
Random rand = new Random();
for (int i = 0; i < codeCount; i++)
{
randomCode += allCharArray[rand.Next(0, allCharLen)];
}
return randomCode;
}
/// <summary>
/// 根据验证码checkCode画图
/// </summary>
/// <param name="checkCode"></param>
private void CreateImage(string checkCode)
{
int iwidth = (int)(checkCode.Length * 11.5);
System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 20);
Graphics g = Graphics.FromImage(image);
Font f = new System.Drawing.Font("Arial", 10, System.Drawing.FontStyle.Bold);
Brush b = new System.Drawing.SolidBrush(Color.White);
//g.FillRectangle(new System.Drawing.SolidBrush(Color.Blue),0,0,image.Width, image.Height);
g.Clear(Color.Blue);
g.DrawString(checkCode, f, b, 3, 3);
g.Dispose();
//Pen blackPen = new Pen(Color.Black, 0);
//Random rand = new Random();
//for (int i = 0; i < 5; i++)
//{
// int y = rand.Next(image.Height);
// g.DrawLine(blackPen, 0, y, image.Width, y);
//}
System.IO.MemoryStream ms = new System.IO.MemoryStream();
image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
Response.ClearContent();
Response.ContentType = "image/Jpeg";
Response.BinaryWrite(ms.ToArray());
image.Dispose();
//---------缓存验证码，以备验证---------
Session["ValidateCode"] = checkCode;
/*如果希望在挂接该aspx页的页面A.aspx内执行Session的绑定就是白扯！
* A页面首先绑定，然后是确定表达式，此时B.aspx未执行，还没有产生Session呢！
* */
}
protected void Page_Load(object sender, EventArgs e)
{
CreateImage(CreateRandomCode(6));
}
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>无标题页</title>
</head>
<body>
</body>
</html>
调用上面的验证程序：
<%@ Page Language="C#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
protected void btnSend_Click(object sender, EventArgs e)
{
if(Session["ValidateCode"].ToString()!=txtValidateCode.Text)
Response.Write("验证码不正确");
else
Response.Write("登录到新的界面！");
}
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>无标题页</title>
</head>
<body>
<form runat="server">
<div>
<asp:TextBox runat="server"></asp:TextBox>
<img src="ValidateCode.aspx" alt="验证码" />
<br />
<asp:Button runat="server" OnClick="btnSend_Click" Text="发送" /></div>
</form>
</body>
</html>
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