Checking if the user is connected to the Internet.

#include <ras.h>
bool IsConnected()
{
   RASCONN TRasCon;
   RASCONNSTATUS Tstatus;

   DWORD lg;
   DWORD lpcon;
   bool lReturn;

   TRasCon.dwSize = 412;
   lg = 256 * TRasCon.dwSize;
   lReturn = false;

   if (RasEnumConnections(&TRasCon, &lg, &lpcon) == 0)
   {
    Tstatus.dwSize = 160;
    RasGetConnectStatus(TRasCon.hrasconn, &Tstatus);
    lReturn = (Tstatus.rasconnstate == 0x2000);
   }
   return(lReturn);
}

 if(IsConnected()) // It's OK.... Connected.. :-)
 else // Not Connected.. :-(


Another way is to use:
#include <intshcut.h>
bool connected = !InetIsOffline(0);