Determine the current network status (C #)

1. Use the internetgetconnectedstate Function

One disadvantage of this function is that it takes several seconds to respond to the problem.

2. Use the isnetworkalive Function

Network connectivity can be reflected in a timely manner, but the System Event Notification Service is required (the system automatically starts the service by default ). To use this function, you must install the latest SDK (for example,. net)

Two methodsCodeAs shown in the following figure, I have tested it from other places.

  [Dllimport (  "  Wininet. dll  "  )]
  Private     Static    Extern     Bool  Internetgetconnectedstate (  Ref     Int  Dwflag,  Int  Dwreserved );

  Private     String  Fun_internetgetconnectedstate ()
{
  Int Internet_connection_modem  =     1  ;
  Int  Internet_connection_lan  =     2  ;
  Int  Internet_connection_proxy  =     4  ;
 Int  Internet_connection_modem_busy  =     8  ;

  String  Output  =     Null  ;
Int32 flags  =     New     Int ();  //  Internet access  
    Bool  M_bonline  =     True  ;  //  Online or not  
  
M_bonline  =  Internetgetconnectedstate ( Ref  Flags,  0  );
  If  (M_bonline)  //  Online  
  {
  If  (Flags  &  Internet_connection_modem)  = Internet_connection_modem)
{
Output  =     "  Online: dial-up Internet access \ n  "  ;
}
  If  (Flags  &  Internet_connection_lan)  =  Internet_connection_lan)
{
Output  =    "  Online: via LAN \ n  "  ;
}
  If  (Flags  &  Internet_connection_proxy)  =  Internet_connection_proxy)
{
Output  =     "  Online: proxy \ n  " ;
}
  If  (Flags  &  Internet_connection_modem_busy)  =  Internet_connection_modem_busy)
{
Output  =     "  Modem is occupied by other non-Internet connections \ n  "  ;
}
}
  Else 
{
Output  =     "  Not online \ n  "  ;
}

  Return  Output;
}


[Dllimport (  "  Sensapi. dll  "  )]
  Private     Extern    Static     Bool  Isnetworkalive (  Out     Int  Connectiondescription );

  Private     String  Fun_isnetworkalive ()
{
  Int  Network_alive_lan  =    0  ;
  Int  Network_alive_wan  =     2  ;
  Int  Network_alive_aol  =     4  ;

  String  Output =     Null  ;
  Int  Flags;  //  Internet access  
    Bool  M_bonline  =     True  ;  //  Online or not 
  
M_bonline  =  Isnetworkalive (  Out  Flags );
  If  (M_bonline)  //  Online  
  {
  If  (Flags  &  Network_alive_lan) =  Network_alive_lan)
{
Output  =     "  Online: network_alive_lan \ n  "  ;
}
  If  (Flags  &  Network_alive_wan)  =  Network_alive_wan)
{
Output  =    "  Online: network_alive_wan \ n  "  ;
}
  If  (Flags  &  Network_alive_aol)  =  Network_alive_aol)
{
Output  =     "  Online: network_alive_aol \ n "  ;
}
}
  Else  
{
Output  =     "  Not online \ n  "  ;
}

  Return  Output;
}

  Private     Void Timereffectick (  Object  Sender, eventargs E)
{
Label1.text  =  Fun_internetgetconnectedstate ();
Label2.text  =  Fun_isnetworkalive ();
}