Ecco come testare lo stato della connessione :

C# :

using System.Runtime.InteropServices ;

public class ConnectionState

  {

    [DllImport("wininet.dll")]
	private extern static bool InternetGetConnectedState(out int Description, int ReservedValue);
	
     public ConnectionState()
    {

    }
	
    public static bool ConnessioneInternet( )//rileva se la macchina è on-line    { 
   { 
     int Desc ; 
     return InternetGetConnectedState( out Desc, 0 ) ; 
    }
  } 

VB.Net :

Imports System.Runtime.InteropServices

Public Class ConnectionState

 <DllImport("wininet.dll")> _
 Private Shared Function InternetGetConnectedState(ByRef Description As Integer, ByVal ReservedValue As Integer) As Boolean
End Function

Public Sub New()
End Sub

Public Shared Function ConnessioneInternet() As Boolean
    Dim Desc As Integer
    Return InternetGetConnectedState(Desc, 0)
End Function


End Class