App: Add auto update check on network change to active

Elwig/App.xaml.cs

@@ -11,6 +11,7 @@ using System.Collections.Generic;
 using System.Data;
 using System.IO;
 using System.Linq;
+using System.Net.NetworkInformation;
 using System.Reflection;
 using System.Text;
 using System.Threading.Tasks;
@@ -131,6 +132,7 @@ namespace Elwig {
                         await CheckForUpdates();
                     });
                 }
+                NetworkChange.NetworkAvailabilityChanged += OnNetworkAvailabilityChanged;
                 _autoUpdateTimer.Tick += new EventHandler(OnAutoUpdateTimer);
                 _autoUpdateTimer.Start();
             }
@@ -228,6 +230,16 @@ namespace Elwig {
             }
         }
 
+        private void OnNetworkAvailabilityChanged(object? sender, NetworkAvailabilityEventArgs evt) {
+            if (!evt.IsAvailable) return;
+            if (Utils.HasInternetConnectivity()) {
+                Utils.RunBackground("Auto Updater", async () => {
+                    await Task.Delay(500);
+                    await CheckForUpdates();
+                });
+            }
+        }
+
         public static async Task CheckForUpdates(bool showAlert = false) {
             if (Config.UpdateUrl == null) return;
             var latest = await Utils.GetLatestInstallerUrl(Config.UpdateUrl);