From a9cede8ed4c5a4ec2ab704178e5036b7a9f61edb Mon Sep 17 00:00:00 2001
From: Joseph Doherty <dohejw01@gmail.com>
Date: Fri, 22 May 2026 07:27:03 -0400
Subject: [PATCH] fix(client-ui): resolve Medium code-review finding
 (Client.UI-005)

Call Subscriptions?.Teardown() and Alarms?.Teardown() in the Disconnected
branch of OnConnectionStateChanged so server-side session drops also
quiesce the DataChanged and AlarmEvent handlers. Add Reattach() methods
that idempotently re-hook the handlers; call them from the Connected
branch so reconnects after a server-side drop restore live updates.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 .../ViewModels/AlarmsViewModel.cs                      | 10 ++++++++++
 .../ViewModels/MainWindowViewModel.cs                  |  4 ++++
 .../ViewModels/SubscriptionsViewModel.cs               | 10 ++++++++++
 3 files changed, 24 insertions(+)

diff --git a/src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/ViewModels/AlarmsViewModel.cs b/src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/ViewModels/AlarmsViewModel.cs
index 42a18a9..d67fd54 100644
--- a/src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/ViewModels/AlarmsViewModel.cs
+++ b/src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/ViewModels/AlarmsViewModel.cs
@@ -215,6 +215,16 @@ public partial class AlarmsViewModel : ObservableObject
         ActiveAlarmCount = 0;
     }
 
+    /// <summary>
+    ///     Re-hooks event handlers to the service after a server-side reconnect.
+    ///     Safe to call when already attached (duplicate += is a no-op in .NET multicast delegates).
+    /// </summary>
+    public void Reattach()
+    {
+        _service.AlarmEvent -= OnAlarmEvent;
+        _service.AlarmEvent += OnAlarmEvent;
+    }
+
     /// <summary>
     ///     Unhooks event handlers from the service.
     /// </summary>
diff --git a/src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/ViewModels/MainWindowViewModel.cs b/src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/ViewModels/MainWindowViewModel.cs
index c757bd6..a3beb9f 100644
--- a/src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/ViewModels/MainWindowViewModel.cs
+++ b/src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/ViewModels/MainWindowViewModel.cs
@@ -166,6 +166,8 @@ public partial class MainWindowViewModel : ObservableObject
         {
             case ConnectionState.Connected:
                 StatusMessage = $"Connected to {EndpointUrl}";
+                Subscriptions?.Reattach();
+                Alarms?.Reattach();
                 break;
             case ConnectionState.Reconnecting:
                 StatusMessage = "Reconnecting...";
@@ -177,6 +179,8 @@ public partial class MainWindowViewModel : ObservableObject
                 StatusMessage = "Disconnected";
                 SessionLabel = string.Empty;
                 RedundancyInfo = null;
+                Subscriptions?.Teardown();
+                Alarms?.Teardown();
                 BrowseTree?.Clear();
                 ReadWrite?.Clear();
                 Subscriptions?.Clear();
diff --git a/src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/ViewModels/SubscriptionsViewModel.cs b/src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/ViewModels/SubscriptionsViewModel.cs
index d4ea3fa..fad17f3 100644
--- a/src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/ViewModels/SubscriptionsViewModel.cs
+++ b/src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/ViewModels/SubscriptionsViewModel.cs
@@ -265,6 +265,16 @@ public partial class SubscriptionsViewModel : ObservableObject
         SubscriptionCount = 0;
     }
 
+    /// <summary>
+    ///     Re-hooks event handlers to the service after a server-side reconnect.
+    ///     Safe to call when already attached (duplicate += is a no-op in .NET multicast delegates).
+    /// </summary>
+    public void Reattach()
+    {
+        _service.DataChanged -= OnDataChanged;
+        _service.DataChanged += OnDataChanged;
+    }
+
     /// <summary>
     ///     Unhooks event handlers from the service.
     /// </summary>