Sunday, June 14, 2009

Check Internet Connection in .net

How to check internet connection in .net application?

For checking Internet connection in .NET application, we can use GetIsNetworkAvailable method defined in the System.Net.Network-Information namespace. But it returns a Boolean value that denotes whether any network connection is available and does not say about Internet connectivity. To make sure we also have Internet access, the reliable method is to attempt to ping a host


using System.Net.NetworkInformation;

public bool IsInternet_Connected()
{
string hostName = "http://www.google.com";
bool bl_result = false;
Ping p = new Ping();
try
{
PingReply ping_reply = p.Send(hostName, 3000);
if (ping_reply.Status == IPStatus.Success)
return true;
}
catch (Exception ex)

{

throw ex;

}


return bl_result;
}


We can also use a simple API function InternetGetConnectedState. This function takes two arguments:

The first one is an integer used with out keyword, which means that after calling the function, the variable will contain an integer that describes the connection state.

The second one is a reserved variable that must be set to 0.

using System ;
using System.Runtime ;
using System.Runtime.InteropServices ;
public class cls_Internet
{

//Create the extern function...
[DllImport("wininet.dll")]
private extern static bool InternetGetConnectedState( out intDescription, int ReservedValue ) ;

//Create a function that uses the API function...
public static bool IsInternet_Connected( )
{

try

{
int Desc ;
return InternetGetConnectedState( out Desc, 0 ) ;

}

catch(Exception ex)

{

throw ex;

}


}
}

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