如何在连接网络时以及用户登录时接收事件

我有一个运行的服务,我希望在以下情况下收到通知:

a)网络已连接.

b)当用户登录机器时.

我怎样才能做到这一点？(C#.NET 2.0)

//using Microsoft.Win32;
//using System.Net.NetworkInformation;
public class SessionChanges
{
    public SessionChanges()
    {
        NetworkChange.NetworkAvailabilityChanged += 
            new NetworkAvailabilityChangedEventHandler(NetworkChange_NetworkAvailabilityChanged);
        SystemEvents.SessionSwitch += new SessionSwitchEventHandler(SystemEvents_SessionSwitch);
    }

    void SystemEvents_SessionSwitch(object sender, SessionSwitchEventArgs e)
    {
        if (e.Reason == SessionSwitchReason.SessionLogon)
        { 
            //user logged in
        }
    }

    void NetworkChange_NetworkAvailabilityChanged(object sender, NetworkAvailabilityEventArgs e)
    {
        if (e.IsAvailable)
        { 
            //a network is available
        }
    }
}