Asp.net实现验证码

<%

//设置页面不缓存

response.setHeader("Pragma", "No-cache");

response.setHeader("Cache-Control", "no-cache");

response.setDateHeader("Expires", 0);

//生成随机类

Random random = new Random();

// 取随机产生的认证码(4位数字)

String sRand = "";

for (int i = 0; i < 4; i++) {

String rand = String.valueOf(random.nextInt(10));

sRand += rand;

}

// 将认证码存入SESSION

session.setAttribute("rand", sRand);

out.print("  <em><font size=3 color=#22dd3f>"+sRand+"</font></em>");

%>