Improve event cleanup, thread safety, and error handling

---
- 🧹 Implement IDisposable in DocumentEvents for proper unsubscription from RunningDocumentTable
- 🧵 Use a single _syncLock in TableDataSource for thread-safe access to collections
- 🛡️ Wrap InfoBar host addition in try-catch and clean up COM event subscription on failure
- ✂️ Simplify SolutionEvents.OnBeforeCloseSolution by removing unnecessary UI thread check and solution retrieval
- 🧩 Update usings to include required Visual Studio namespaces

Author: madskristensen

src/toolkit/Community.VisualStudio.Toolkit.Shared/Documents/DocumentEvents.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using Microsoft.VisualStudio;
 using Microsoft.VisualStudio.Shell;
 using Microsoft.VisualStudio.Shell.Interop;
@@ -18,14 +18,40 @@ public partial class Events
     /// <summary>
     /// Events related to the editor documents.
     /// </summary>
-    public class DocumentEvents : IVsRunningDocTableEvents
+    public class DocumentEvents : IVsRunningDocTableEvents, IDisposable
     {
         private readonly RunningDocumentTable _rdt;
+        private readonly uint _adviseCookie;
+        private bool _disposed;
 
         internal DocumentEvents()
         {
             _rdt = new RunningDocumentTable();
-            _rdt.Advise(this);
+            _adviseCookie = _rdt.Advise(this);
+        }
+
+        /// <summary>
+        /// Disposes the document events and unsubscribes from the running document table.
+        /// </summary>
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        /// <summary>
+        /// Disposes the document events and unsubscribes from the running document table.
+        /// </summary>
+        protected virtual void Dispose(bool disposing)
+        {
+            if (!_disposed)
+            {
+                if (disposing)
+                {
+                    _rdt.Unadvise(_adviseCookie);
+                }
+                _disposed = true;
+            }
         }
 
         /// <summary>

src/toolkit/Community.VisualStudio.Toolkit.Shared/ErrorList/TableDataSource.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using Microsoft;
@@ -25,6 +25,11 @@ public TableDataSource(string name)
             Initialize();
         }
 
+        /// <summary>
+        /// Single lock object for thread-safe access to _managers and _snapshots
+        /// </summary>
+        private readonly object _syncLock = new();
+
         /// <summary>
         /// Data sink subscriptions
         /// </summary>
@@ -91,7 +96,7 @@ protected void Initialize()
         /// <param name="manager">Subscription to register</param>
         private void AddSinkManager(SinkManager manager)
         {
-            lock (_managers)
+            lock (_syncLock)
             {
                 _managers.Add(manager);
             }
@@ -103,7 +108,7 @@ private void AddSinkManager(SinkManager manager)
         /// <param name="manager">Subscription to unregister</param>
         private void RemoveSinkManager(SinkManager manager)
         {
-            lock (_managers)
+            lock (_syncLock)
             {
                 _managers.Remove(manager);
             }
@@ -114,7 +119,7 @@ private void RemoveSinkManager(SinkManager manager)
         /// </summary>
         private void UpdateAllSinks()
         {
-            lock (_managers)
+            lock (_syncLock)
             {
                 foreach (SinkManager manager in _managers)
                 {
@@ -137,7 +142,7 @@ public void AddErrors(IEnumerable<ErrorListItem> errors)
 
             IEnumerable<ErrorListItem> cleanErrors = errors.Where(e => e != null && !string.IsNullOrEmpty(e.FileName));
 
-            lock (_snapshots)
+            lock (_syncLock)
             {
                 foreach (IGrouping<string?, ErrorListItem>? fileErrorMap in cleanErrors.GroupBy(e => e.FileName))
                 {
@@ -164,14 +169,11 @@ public void AddErrors(IEnumerable<ErrorListItem> errors)
         /// </summary>
         public void CleanAllErrors()
         {
-            lock (_snapshots)
+            lock (_syncLock)
             {
-                lock (_managers)
+                foreach (SinkManager manager in _managers)
                 {
-                    foreach (SinkManager manager in _managers)
-                    {
-                        manager.Clear();
-                    }
+                    manager.Clear();
                 }
 
                 foreach (TableEntriesSnapshot snapshot in _snapshots.Values)

src/toolkit/Community.VisualStudio.Toolkit.Shared/Notifications/InfoBar.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Threading.Tasks;
 using System.Windows.Controls;
 using Microsoft.VisualStudio.Shell;
@@ -122,11 +122,18 @@ public async Task<bool> TryShowInfoBarUIAsync()
             _uiElement = infoBarUIFactory.CreateInfoBar(_model);
             _uiElement.Advise(this, out _listenerCookie);
 
-            if (_host != null)
+            try
             {
                 _host.AddInfoBar(_uiElement);
                 IsVisible = true;
             }
+            catch
+            {
+                // If adding to host fails, clean up the COM event subscription to prevent leak
+                _uiElement.Unadvise(_listenerCookie);
+                _uiElement = null;
+                throw;
+            }
 
             return IsVisible;
         }

src/toolkit/Community.VisualStudio.Toolkit.Shared/Solution/SolutionEvents.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using Microsoft.VisualStudio;
 using Microsoft.VisualStudio.Shell;
 using Microsoft.VisualStudio.Shell.Interop;
@@ -167,15 +167,8 @@ int IVsSolutionEvents.OnQueryCloseSolution(object pUnkReserved, ref int pfCancel
 
         int IVsSolutionEvents.OnBeforeCloseSolution(object pUnkReserved)
         {
-            ThreadHelper.ThrowIfNotOnUIThread();
-
-            if (OnBeforeCloseSolution != null)
-            {
-                SolutionItem? solution = VS.Solutions.GetCurrentSolution();
-                OnBeforeCloseSolution?.Invoke();
-            }
+            OnBeforeCloseSolution?.Invoke();
             return VSConstants.S_OK;
-
         }
 
         int IVsSolutionEvents.OnAfterCloseSolution(object pUnkReserved)