ShowMessageAnsync() causes exception

[gordon771]

What steps will reproduce this issue?

Following exception is thrown in ShowMessageAsync() after update from MahApps.Metro V1.3.0 to V1.4.2:

System.InvalidOperationException wurde nicht von Benutzercode behandelt.
  HResult=-2146233079
  Message=The calling thread cannot access this object because a different thread owns it.
  Source=WindowsBase
  StackTrace:
       at System.Windows.Threading.Dispatcher.VerifyAccess()
       at System.Windows.Application.get_MainWindow()
       at MahApps.Metro.Controls.Dialogs.BaseMetroDialog.DetectTheme(DependencyObject dialog) in d:\projects\git\MahApps.Metro\src\MahApps.Metro\MahApps.Metro.Shared\Controls\Dialogs\BaseMetroDialog.cs:line 229
       at MahApps.Metro.Controls.Dialogs.BaseMetroDialog.HandleTheme() in d:\projects\git\MahApps.Metro\src\MahApps.Metro\MahApps.Metro.Shared\Controls\Dialogs\BaseMetroDialog.cs:line 155
       at MahApps.Metro.Controls.Dialogs.BaseMetroDialog.Initialize(MetroWindow owningWindow, MetroDialogSettings settings) in d:\projects\git\MahApps.Metro\src\MahApps.Metro\MahApps.Metro.Shared\Controls\Dialogs\BaseMetroDialog.cs:line 135
       at MahApps.Metro.Controls.Dialogs.BaseMetroDialog..ctor(MetroWindow owningWindow, MetroDialogSettings settings) in d:\projects\git\MahApps.Metro\src\MahApps.Metro\MahApps.Metro.Shared\Controls\Dialogs\BaseMetroDialog.cs:line 93
       at MahApps.Metro.Controls.Dialogs.MessageDialog..ctor(MetroWindow parentWindow, MetroDialogSettings settings) in d:\projects\git\MahApps.Metro\src\MahApps.Metro\MahApps.Metro.Shared\Controls\Dialogs\MessageDialog.cs:line 27
       at MahApps.Metro.Controls.Dialogs.DialogManager.<>c__DisplayClass2_0.<ShowMessageAsync>b__1() in d:\projects\git\MahApps.Metro\src\MahApps.Metro\MahApps.Metro.Shared\Controls\Dialogs\DialogManager.cs:line 164
       at System.Windows.Threading.DispatcherOperation`1.InvokeDelegateCore()
       at System.Windows.Threading.DispatcherOperation.InvokeImpl()

The ShowMessageAsync() has to be shown in a sub MetroWindow. The sub window is running within his own thread and Dispatcher context:

Thread thread = new Thread(() =>
	{                                       
		SynchronizationContext.SetSynchronizationContext(new DispatcherSynchronizationContext(Dispatcher.CurrentDispatcher));  // create and install a context

		WindowBase dialog    = (WindowBase)dllAssembly.CreateInstance(dialogClass);					
		dialog.Show();					      

		Dispatcher.Run();                   
	});

thread.SetApartmentState(ApartmentState.STA);
thread.IsBackground = false;

thread.Start(); 

So the access to the applications main window (System.Windows.Application.get_MainWindow()) is problematic. My code is working with V1.3.0 of MahApps flawless.

Expected outcome

Same behaviour like in previous major version 1.3.0 => no exception

--

Environment

• MahApps.Metro v1.4.2
• Windows 7
• Visual Studio 2013
• .NET Framework 4.6.2

--

Thank you!!!

Thank you very much for your amazing and absolutely impressiv GUI framework, which is gives the right touch to the standard WPF GUI._

[punker76]

@gordon771 Can you provide your app or create a short sample? Would be helpful. thx

[gordon771]

Hi,

I created a small VS project where you can reproduce the exception. How can I provide it to you?

[punker76]

@gordon771 put it on GutHub or drop a zip here as comment

[gordon771]

Here it comes...
MahAppsProblem.zip