方法一：
string postData = string.Format("a=1&b=2"); //post传递参数
Stream outstream = null;
Stream instream = null;
StreamReader sr = null;
HttpWebResponse response = null;
HttpWebRequest request = null;
Encoding encoding = Encoding.Default;
byte[] data = encoding.GetBytes(postData);
// 准备请求
// 设置参数
request = WebRequest.Create("http://www.baidu.com") as HttpWebRequest;
CookieContainer cookieContainer = new CookieContainer();
request.CookieContainer = cookieContainer;
request.AllowAutoRedirect = true;
request.Method = "POST";
request.ContentType = "application/x-www-form-urlencoded";
request.ContentLength = data.Length;
outstream = request.GetRequestStream();
outstream.Write(data, 0, data.Length);
outstream.Close();
//发送请求并获取相应回应数据
在Web编程过程中，存在着很多安全隐患。比如在以前的ASP版本中，Cookie为访问者和编程者都提供了方便，并没有提供加密的功能。打开IE浏览器，选择“工具”菜单里的“Internet选项”，然后在弹出的对话框里单击“设置”按钮，选择“查看文件”按钮，在弹出的窗口中，就会显示硬盘里 ......
asp.net输出 png 32位 图像，带透明alpha。
// pngtest.htm
<html>
<head></head>
<body bgColor="gray">
<img src="png.ashx" />
</body>
</html>
// png.ashx
<%@ WebHandler Language="C#" Class="Png" %>
using System.Web;
public class Png : IHtt ......
