Detect network changes in Xamarin Forms - xamarin

Question

I want to detect when the user is online or offline.
I am using CrossConnectivity package to detect connectivity changes.
I have to connect to VPN (Sonic Wall to be exact) in order to connect to my server.
My problem is this: When I am connecting to my server, I need to switch apps in order for me to connect to my server. When I switch back to my app the function SyncFunction.SyncUser(host, database, contact, ipaddress, pingipaddress) is not executing. The connectivity changed function is not on my App.xaml.cs it is on my Main Menu Content page because I need the sync function to be executed in my main menu not the whole app. How can I fix this?
CrossConnectivity.Current.ConnectivityChanged += async (sender, args) =>
{
var appdate = Preferences.Get("appdatetime", String.Empty, "private_prefs");
if (string.IsNullOrEmpty(appdate))
{
Preferences.Set("appdatetime", DateTime.Now.ToString(), "private_prefs");
}
else
{
if (DateTime.Now >= DateTime.Parse(Preferences.Get("appdatetime", String.Empty, "private_prefs")))
{
Preferences.Set("appdatetime", DateTime.Now.ToString(), "private_prefs");
if (CrossConnectivity.Current.IsConnected)
{
var ping = new Ping();
var reply = ping.Send(new IPAddress(pingipaddress), 5000);
if (reply.Status == IPStatus.Success)
{
lblStatus.Text = "Syncing data to server";
lblStatus.BackgroundColor = Color.FromHex("#2bcbba");
await Task.Delay(5000);
SyncFunction.SyncUser(host, database, contact, ipaddress, pingipaddress);
lblStatus.Text = "Online - Connected to server";
lblStatus.BackgroundColor = Color.FromHex("#2ecc71");
}
else
{
lblStatus.Text = "Online - Server unreachable. Connect to VPN";
lblStatus.BackgroundColor = Color.FromHex("#e67e22");
}
}
else
{
lblStatus.Text = "Offline - Connect to internet";
lblStatus.BackgroundColor = Color.FromHex("#e74c3c");
}
}
else
{
await DisplayAlert("Application Error", "It appears you change the time/date of your phone. Please restore the correct time/date", "Got it");
await Navigation.PopToRootAsync();
}
}
};

Answer 1

Detecting connectivity change across a VPN is not easy.
A workaround solution is to use a webservice as ping.
If you have a backend with API, this "ping" can be executed regularly to ensure the network AND the API are accessible.
This solution is to be used in addition to the connectivity check
Subscribe to connectivity changed
When conectivity looks OK, check the "ping service"
Typically in a mob app, this "ping endpoint" can be something like "/about".
Moreover, this specific service can be use to perform the compatibility version check beetween App Mob version and API version.
(look also Xamarin.Essentials to replace CrossConnectivity by Xamarin.Essentials: Connectivity, https://learn.microsoft.com/fr-fr/xamarin/essentials/connectivity?context=xamarin%2Fxamarin-forms&tabs=android)