こんにちは私はこれをメインに持っています
NetworkChange.NetworkAddressChanged += new NetworkAddressChangedEventHandler(AddressChangedCallback);
//The main also contains a form
そしてその下のこのメソッド。
static void AddressChangedCallback(object sender, EventArgs e){
// would like to have a message box here that freezes the entire application
including the form as mentioned above , untill OK is pressed"
}