ThemeManager.Current.SystemThemeChanged throws TargetInvocationException (NullReferenceException)

[CodingOctocat]

Describe the bug

This is a strange issue: if I subscribe to the ThemeManager.Current.SystemThemeChanged event, toggling "Hidden items" in File Explorer causes an exception to occur.

Timestamp: 2025/12/8 10:01:08
OSVersion: Microsoft Windows NT 10.0.26200.0
ClrVersion: 10.0.0
ThreadName: N/A(2)
----------------------------------------
Handler: DispatcherUnhandledException
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Type: System.Reflection.TargetInvocationException
Source: System.Private.CoreLib
Message: Exception has been thrown by the target of an invocation.
TargetSite: System.Object InvokeWithFewArgs(System.Object, System.Reflection.BindingFlags, System.Reflection.Binder, System.Object[], System.Globalization.CultureInfo)
StackTrace:
   at System.Reflection.MethodBaseInvoker.InvokeWithFewArgs(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Delegate.DynamicInvokeImpl(Object[] args)
   at Microsoft.Win32.SystemEvents.SystemEventInvokeInfo.InvokeCallback(Object arg)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
HResult: -2146232828
HelpLink: null

--- Inner Exception (Level 1) ---
Type: System.NullReferenceException
Source: HandyControl
Message: Object reference not set to an instance of an object.
TargetSite: Void <SystemEvents_UserPreferenceChanged>b__32_0()
StackTrace:
   at HandyControl.Themes.ThemeManager.<SystemEvents_UserPreferenceChanged>b__32_0()
   at HandyControl.Tools.DispatcherHelper.RunOnUIThread(DispatcherObject d, Action action)
   at HandyControl.Tools.DispatcherHelper.RunOnMainThread(Action action)
   at HandyControl.Themes.ThemeManager.SystemEvents_UserPreferenceChanged(Object sender, UserPreferenceChangedEventArgs e)
   at InvokeStub_UserPreferenceChangedEventHandler.Invoke(Object, Span`1)
   at System.Reflection.MethodBaseInvoker.InvokeWithFewArgs(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
HResult: -2147467261
HelpLink: null
InnerException: null

Steps to reproduce the bug

1. Subscribe ThemeManager.Current.SystemThemeChanged += (_, _)=> { // NOP. };
2. Open File Explorer, and toggle "Hidden items"

   

3. Throw TargetInvocationException (NullReferenceException)

Expected behavior

No response

Screenshots

No response

NuGet package version

HandyControl 3.6.0

IDE

Visual Studio 2026

Framework type

.Net 10.0

Windows version

Windows 11 (25H2) - 26200.6584

Additional context

No response