方法1：
HttpBaseProtocolFilter filter = new HttpBaseProtocolFilter();
var cookis = filter.CookieManager.GetCookies("http://dy.qq.com/passport/loginSuccess.htm");
方法2：
string InternetGetCookieEx(string url)
{
uint sizeInBytes = 0;
// Gets capacity length first
InternetGetCookieEx(url, null, null, ref sizeInBytes, INTERNET_COOKIE_HTTPONLY, IntPtr.Zero);
uint bufferCapacityInChars = (uint)Encoding.Unicode.GetMaxCharCount((int)sizeInBytes);
// Now get cookie data
var cookieData = new StringBuilder((int)bufferCapacityInChars);
InternetGetCookieEx(url, null, cookieData, ref bufferCapacityInChars, INTERNET_COOKIE_HTTPONLY, IntPtr.Zero);
return cookieData.ToString();
}
const int INTERNET_COOKIE_HTTPONLY = 0x00002000;
[DllImport("wininet.dll", CharSet = CharSet.Unicode, SetLastError = true)]
static extern bool InternetGetCookieEx(string pchURL, string pchCookieName, StringBuilder pchCookieData, ref System.UInt32 pcchCookieData, int dwFlags, IntPtr lpReserved);