C#

// Checks if Network is either connected by LAN or Wireless
        public bool IsNetworkConnected()
        {
            NetworkInterface[] networkCards = NetworkInterface.GetAllNetworkInterfaces();
            bool connected = false;

            // Loop through to find the one we want to check for connectivity.
            // Connection can have different numbers appended so check that the 
            // network connections start with the conditions checked below.
            foreach (NetworkInterface nc in networkCards)
            {
                // Check LAN
                if (nc.Name.StartsWith("Local Area Connection"))
                {
                    if (nc.OperationalStatus == OperationalStatus.Up)
                    {
                        connected = true;
                    }
                }

                // Check for Wireless
                if (nc.Name.StartsWith("Wireless Network Connection"))
                {
                    if (nc.OperationalStatus == OperationalStatus.Up)
                    {
                        connected = true;
                    }
                }
            }

            return connected;
        }