Implement fallbacks for empty, null, or nonexistent in managed runtim…

…e class names. (#218)

WinRT.Runtime/ComWrappersSupport.cs

@@ -267,6 +267,11 @@ private static Func<IInspectable, object> CreateArrayFactory(Type implementation
 
  internal static Func<IInspectable, object> CreateTypedRcwFactory(string runtimeClassName)
  {
+ // If we don't have a runtime class name, then we just use IInspectable.
+ if (string.IsNullOrEmpty(runtimeClassName))
+ {
+ return (IInspectable obj) => obj;
+ }
  // PropertySet and ValueSet can return IReference<String> but Nullable<String> is illegal
  if (runtimeClassName == "Windows.Foundation.IReference`1<String>")
  {
@@ -277,7 +282,18 @@ internal static Func<IInspectable, object> CreateTypedRcwFactory(string runtimeC
  return (IInspectable obj) => new ABI.System.Nullable<Type>(obj.ObjRef);
  }
 
- var (implementationType, _) = TypeNameSupport.FindTypeByName(runtimeClassName.AsSpan());
+ Type implementationType = null;
+
+ try
+ {
+ (implementationType, _) = TypeNameSupport.FindTypeByName(runtimeClassName.AsSpan());
+ }
+ catch (TypeLoadException)
+ {
+ // If we reach here, then we couldn't find a type that matches the runtime class name.
+ // Fall back to using IInspectable directly.
+ return (IInspectable obj) => obj;
+ }
 
  if (implementationType.IsGenericType && implementationType.GetGenericTypeDefinition() == typeof(System.Collections.Generic.KeyValuePair<,>))
  {

WinUI/WinUIDesktopSample/App.xaml.cs

@@ -22,6 +22,7 @@ public App()
  Window myWindow;
  protected override void OnLaunched(LaunchActivatedEventArgs args)
  {
+ var value = DependencyProperty.UnsetValue;
  var button = new Button
  {
  Content = "Click me to load MainPage",