Wpf toolkit MessageBox style exception

Question

I use Xceed.Wpf.Toolkit.MessageBox to show a dialog, and I need to set the style dynamically.

When I have access to the UI dispatcher I simply call the Show() method passing the style as an argument and everything goes right.

But when I don't have access to the UI thread I write

Application.Current.Dispatcher.Invoke(DispatcherPriority.Normal, new Action(() =>
{
    MessageBox.Show("Message Text", ..., myStyle);
}));

And by doing this I get an exception:

The calling thread cannot access this object because a different thread owns it.

Of course when removing the style from the arguments, no exception gets thrown.
myStyle is created directly in the method, is not passed from another thread or something.

Does anyone know why this happens and how to resolve the issue?

Stack Trace:

at System.Windows.Threading.Dispatcher.VerifyAccess()
at System.Windows.Style.CheckTargetType(Object element)
at System.Windows.StyleHelper.UpdateStyleCache(FrameworkElement fe, FrameworkContentElement fce, Style oldStyle, Style newStyle, Style& styleCache)
at System.Windows.FrameworkElement.OnStyleChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
at System.Windows.DependencyObject.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
at System.Windows.FrameworkElement.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
at System.Windows.DependencyObject.NotifyPropertyChange(DependencyPropertyChangedEventArgs args)
at System.Windows.DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, Boolean coerceWithDeferredReference, Boolean coerceWithCurrentValue, OperationType operationType)
at System.Windows.DependencyObject.SetValueCommon(DependencyProperty dp, Object value, PropertyMetadata metadata, Boolean coerceWithDeferredReference, Boolean coerceWithCurrentValue, OperationType operationType, Boolean isInternal)
at System.Windows.DependencyObject.SetValue(DependencyProperty dp, Object value)
at Xceed.Wpf.Toolkit.MessageBox.ShowCore(Window owner, IntPtr ownerHandle, String messageText, String caption, MessageBoxButton button, MessageBoxImage icon, MessageBoxResult defaultResult, Style messageBoxStyle)
at Xceed.Wpf.Toolkit.MessageBox.Show(Window owner, String messageText, String caption, MessageBoxButton button, MessageBoxImage icon, MessageBoxResult defaultResult, Style messageBoxStyle)
at MyNamespace.MyClass.<>c__DisplayClass1_0.<MyMethod>b__4() in C:\MyFile.cs:line 94
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)
at System.Windows.Threading.DispatcherOperation.InvokeImpl()
at MS.Internal.CulturePreservingExecutionContext.CallbackWrapper(Object obj)
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at MS.Internal.CulturePreservingExecutionContext.Run(CulturePreservingExecutionContext executionContext, ContextCallback callback, Object state)
at System.Windows.Threading.DispatcherOperation.Invoke()
at System.Windows.Threading.Dispatcher.ProcessQueue()
at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
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)
at System.Windows.Threading.Dispatcher.LegacyInvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs)
at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg)
at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame)
at System.Windows.Window.ShowHelper(Object booleanBox)
at System.Windows.Window.ShowDialog()

mm8 mm8 · Accepted Answer · 2019-04-11T15:13:31

You can't create myStyle on the background thread and then apply it to a control on the dispatcher thread. You need to create it on the same dispatcher thread:

Application.Current.Dispatcher.Invoke(DispatcherPriority.Normal, new Action(() =>
{
    //create myStyle here...
    var myStyle = ...;
    MessageBox.Show("Message Text", ..., myStyle);
}));

Wpf toolkit MessageBox style exception

1 Answers