一、前台Js方式调用（base64.js自己在网上找吧，就不上贴了）
<html>
<head>
<title></title>
<script language="javascript" type="text/javascript" src="base64.js" ></script></head>
<body>
<div>
<textarea id="the_code" style="800px; height:160px;">1233333334455</textarea><br>
<input type="submit" onclick="document.all('the_code').value=encode64(document.all('the_code').value);" value="BASE64加密">
<input type="submit" onclick="document.all('the_code').value=decode64(document.all('the_code').value);" value="BASE64解密">
</div>
</body>
</html>
二、后台Cs应用
using System.Text;
using System.IO;
using System.Security.Cryptography;
//*******加密**********//
Convert.ToBase64String(System.Text.UTF8Encoding.Default.GetBytes(Value));
//*******解密**********//
System.Text.UTF8Encoding.Default.GetString(Convert.FromBase64String(Value));