Fix GC issues with static events. (#759)

src/Tests/UnitTest/TestComponentCSharp_Tests.cs

@@ -2305,6 +2305,28 @@ public void TestCovariance()
  Assert.True(TestObject.IterableOfObjectIterablesProperty.SequenceEqual(listOfListOfUris));
  }
 
+ [Fact]
+ public void TestStaticEventWithGC()
+ {
+ bool eventCalled = false;
+ void Class_StaticIntPropertyChanged(object sender, int e)
+ {
+ eventCalled = (e == 3);
+ }
+
+ Class.StaticIntPropertyChanged += Class_StaticIntPropertyChanged;
+ GC.Collect(2, GCCollectionMode.Forced, true);
+ GC.WaitForPendingFinalizers();
+ Class.StaticIntPropertyChanged -= Class_StaticIntPropertyChanged;
+ Class.StaticIntProperty = 3;
+ Assert.False(eventCalled);
+ Class.StaticIntPropertyChanged += Class_StaticIntPropertyChanged;
+ GC.Collect(2, GCCollectionMode.Forced, true);
+ GC.WaitForPendingFinalizers();
+ Class.StaticIntProperty = 3;
+ Assert.True(eventCalled);
+ }
+
 #if NET5_0
  [TestComponentCSharp.Warning] // NO warning CA1416
  class WarningManaged { };

src/cswinrt/code_writers.h

@@ -1545,9 +1545,29 @@ remove => %.% -= value;
 
  std::string write_static_cache_object(writer& w, std::string_view cache_type_name, TypeDef const& class_type)
  {
- if (settings.netstandard_compat)
+ bool hasStaticEvent = false;
+ for (auto&& evt : class_type.EventList())
  {
-
+ auto [add, _] = get_event_methods(evt);
+ if (add.Flags().Static())
+ {
+ hasStaticEvent = true;
+ break;
+ }
+ }
+
+ auto instance = hasStaticEvent ?
+ w.write_temp(
+ "private static readonly _% _instance = new _%();",
+ cache_type_name,
+ cache_type_name) :
+ w.write_temp(
+ "private static readonly WeakLazy<_%> _instance = new WeakLazy<_%>();",
+ cache_type_name,
+ cache_type_name);
+
+ if (settings.netstandard_compat)
+ { 
  auto cache_vftbl_type = w.write_temp("ABI.%.%.Vftbl",
  class_type.TypeNamespace(),
  cache_type_name);
@@ -1562,18 +1582,18 @@ remove => %.% -= value;
 internal class _% : ABI.%.%
 {
 public _%() : base(%()) { }
-private static WeakLazy<_%> _instance = new WeakLazy<_%>();
-internal static % Instance => _instance.Value;
+%
+internal static % Instance => %;
 }
 )",
  cache_type_name,
  class_type.TypeNamespace(),
  cache_type_name,
  cache_type_name,
  cache_interface,
+ instance,
  cache_type_name,
- cache_type_name,
- cache_type_name);
+ hasStaticEvent ? "_instance" : "_instance.Value");
  }
  else
  {
@@ -1586,8 +1606,8 @@ public _%()
 _obj = (new BaseActivationFactory("%", "%.%"))._As(GuidGenerator.GetIID(typeof(%.%).GetHelperType()));
 }
 
-private static WeakLazy<_%> _instance = new WeakLazy<_%>();
-internal static % Instance => (%)_instance.Value;
+%
+internal static % Instance => (%)%;
 
 IObjectReference IWinRTObject.NativeObject => _obj;
 bool IWinRTObject.HasUnwrappableNativeObject => false;
@@ -1602,10 +1622,10 @@ global::System.Collections.Concurrent.ConcurrentDictionary<RuntimeTypeHandle, ob
  class_type.TypeName(),
  class_type.TypeNamespace(),
  cache_type_name,
+ instance,
  cache_type_name,
  cache_type_name,
- cache_type_name,
- cache_type_name);
+ hasStaticEvent ? "_instance" : "_instance.Value");
  }
 
  return w.write_temp("_%.Instance", cache_type_name);