C#

bool internetAvailable = false;
 
Ping pinger = new Ping();
PingOptions pingOptions = new PingOptions(1, true);
byte[] pingResults = new byte[2];
 
PingReply pingReply = pinger.Send("www.microsoft.com", 25000, pingResults, pingOptions);
if (pingReply.Status == IPStatus.Success)
{
   internetAvailable = true;
}

bool internetAvailable = false;
 
Uri requestUri = new UriBuilder("http", "www.microsoft.com").Uri;
HttpWebRequest connectivityCheck = WebRequest.Create(requestUri) as HttpWebRequest;
 
// A Domain Name System (DNS) query may take up to 15 seconds to return or time out, so
// set the timeout to 25 seconds.
connectivityCheck.Timeout = 25000;
 
HttpWebResponse connectivityResponse = connectivityCheck.GetResponse() as HttpWebResponse;
if (connectivityResponse.StatusCode == HttpStatusCode.OK)
{
   if (!connectivityResponse.IsFromCache)
   {
      internetAvailable = true;
   }
}