Fix SA1214 and IDISP003 analyzer violations in SampleContainer (#564)

* Initial plan

* Fix SA1214 and IDISP003 analyzer errors in SampleContainer

Co-authored-by: weiyuanyue <176483933+weiyuanyue@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: weiyuanyue <176483933+weiyuanyue@users.noreply.github.com>

Author: Copilot

AIDevGallery/Controls/SampleContainer.xaml.cs

@@ -58,14 +58,14 @@ public List<string> NugetPackageReferences
     public static readonly DependencyProperty NugetPackageReferencesProperty =
         DependencyProperty.Register("NugetPackageReferences", typeof(List<string>), typeof(SampleContainer), new PropertyMetadata(null));
 
+    private readonly object _ctsLock = new object();
     private RichTextBlockFormatter codeFormatter;
     private Dictionary<string, string> codeFiles = new();
     private Sample? _sampleCache;
     private Dictionary<ModelType, ExpandedModelDetails>? _cachedModels;
     private List<ModelDetails>? _modelsCache;
     private WinMlSampleOptions? _currentWinMlSampleOptions;
     private CancellationTokenSource? _sampleLoadingCts;
-    private readonly object _ctsLock = new object();
     private TaskCompletionSource? _sampleLoadedCompletionSource;
     private double _codePaneWidth;
     private ModelType? _wcrApi;
@@ -119,10 +119,14 @@ private void CancelCTS()
 
         if (cts != null)
         {
-            using (cts)
+            try
             {
                 cts.Cancel();
             }
+            finally
+            {
+                cts.Dispose();
+            }
         }
     }