Try This
using System.Net.NetworkInformation;
namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{
public Form1()
{
}
private void button1_Click(object sender, EventArgs e)
{
NetworkChange.NetworkAvailabilityChanged += new NetworkAvailabilityChangedEventHandler(NetworkChange_NetworkAvailabilityChanged);
}
public void NetworkChange_NetworkAvailabilityChanged(Object sender, NetworkAvailabilityEventArgs e)
{
if (e.IsAvailable)
MessageBox.Show("Connected");
else
MessageBox.Show("Disconnected");
}
}
}