获取Cookie（未测试）

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;

namespace Cookie
{
    class Program
    {
        [DllImport("wininet.dll", CharSet = CharSet.Auto, SetLastError = true)]
        static extern bool InternetGetCookieEx(string pchURL, string pchCookieName, StringBuilder pchCookieData, ref System.UInt32 pcchCookieData, int dwFlags, IntPtr lpReserved);
        [DllImport("wininet.dll", CharSet = CharSet.Auto, SetLastError = true)]
        static extern int InternetSetCookieEx(string lpszURL, string lpszCookieName, string lpszCookieData, int dwFlags, IntPtr dwReserved);

        static void Main(string[] args)
        {
            String cookie = GetCookies("http://www.baidu.com/");
            Console.WriteLine(cookie);
        }

        public static string GetCookies(string url)
        {
            uint datasize = 256;
            StringBuilder cookieData = new StringBuilder((int)datasize);
            if (!InternetGetCookieEx(url, null, cookieData, ref datasize, 0x2000, IntPtr.Zero))
            {
                if (datasize < 0)
                    return null;
                cookieData = new StringBuilder((int)datasize);
                if (!InternetGetCookieEx(url, null, cookieData, ref datasize, 0x00002000, IntPtr.Zero))
                    return null;
            }
            return cookieData.ToString();
        }
    }
}