如何从任务/线程访问TextBlock控件？

Question

I need to update a UI control from within a task/thread. What am I doing wrong here? Trying to write some debug info to a page instead of just the Visual Studio output console.

MySuperAppPage::MySuperAppPage(){
    // in main thread
    InitializeComponent();
    this->myTextBlock->Text = "mainThread"; // works 

    create_task([this]() // async
    {   
        while(true) {
            OutputDebugString(L"thread2\n"); // works
            this->myTextBlock->Text = "thread2"; // failed 
            Sleep(1000);         
        }   
    });  
}

error returned : Unhandled exception at 0x00007FFB2939D01B (Windows.UI.Xaml.dll) in test-uwp.exe: 0xC000027B: An application-internal exception has occurred (parameters: 0x000001DDE95257E0, 0x0000000000000003).

EDIT:

Callstack:

    KernelBase.dll!RaiseFailFastException() Unknown
    combase.dll!RoFailFastWithErrorContextInternal2(HRESULT hrError, unsigned long cStowedExceptions, _STOWED_EXCEPTION_INFORMATION_V2 * * aStowedExceptionPointers) Line 1034  C++
    Windows.UI.Xaml.dll!DirectUI::ErrorHelper::ProcessUnhandledError(DirectUI::ErrorInfo & errorInfo, unsigned int fSkipFailFastIfNoErrorContext, unsigned int * pfHandled) Line 617    C++
    Windows.UI.Xaml.dll!DirectUI::FinalUnhandledErrorDetectedRegistration::OnFinalUnhandledErrorDetected(IInspectable * pSender, Windows::ApplicationModel::Core::IUnhandledErrorDetectedEventArgs * pArgs) Line 975    C++
>   Windows.UI.Xaml.dll!Microsoft::WRL::Details::InvokeHelper<Microsoft::WRL::Implements<Microsoft::WRL::RuntimeClassFlags<2>,Windows::Foundation::IEventHandler<Windows::ApplicationModel::Core::UnhandledErrorDetectedEventArgs * __ptr64>,Microsoft::WRL::FtmBase,Microsoft::WRL::Details::Nil,Microsoft::WRL::Details::Nil,Microsoft::WRL::Details::Nil,Microsoft::WRL::Details::Nil,Microsoft::WRL::Details::Nil,Microsoft::WRL::Details::Nil,Microsoft::WRL::Details::Nil>,long (__cdecl*)(IInspectable * __ptr64,Windows::ApplicationModel::Core::IUnhandledErrorDetectedEventArgs * __ptr64),2>::Invoke(IInspectable * arg1, Windows::ApplicationModel::Core::IUnhandledErrorDetectedEventArgs * arg2) Line 274 C++
    twinapi.appcore.dll!Windows::Internal::Details::GitInvokeHelper<struct Windows::Foundation::IEventHandler<class Windows::ApplicationModel::Core::UnhandledErrorDetectedEventArgs *>,class Windows::Internal::GitPtr,2>::Invoke(struct IInspectable *,struct Windows::ApplicationModel::Core::IUnhandledErrorDetectedEventArgs *)    Unknown
    twinapi.appcore.dll!Windows::ApplicationModel::Core::UnhandledErrorInvokeHelper::Invoke(struct IInspectable *,struct Windows::ApplicationModel::Core::IUnhandledErrorDetectedEventArgs *)   Unknown
    twinapi.appcore.dll!Microsoft::WRL::InvokeTraits<2>::InvokeDelegates<class <lambda_c38a937a821308c18b1a725c966ecfa2>,struct Windows::Foundation::IEventHandler<class Windows::ApplicationModel::Core::UnhandledErrorDetectedEventArgs *> >(class <lambda_c38a937a821308c18b1a725c966ecfa2>,class Microsoft::WRL::Details::EventTargetArray *,class Microsoft::WRL::EventSource<struct Windows::Foundation::IEventHandler<class Windows::ApplicationModel::Core::UnhandledErrorDetectedEventArgs *>,struct Microsoft::WRL::InvokeModeOptions<2> > *) Unknown
    twinapi.appcore.dll!`wil::ErrorHandlingHelpers::Instance(void)'::`2'::`dynamic atexit destructor for 'wrapper''(void)   Unknown
    twinapi.appcore.dll!Windows::ApplicationModel::Core::CoreApplication::ForwardLocalError(struct IRestrictedErrorInfo *)  Unknown
    twinapi.appcore.dll!Windows::ApplicationModel::Core::CoreApplicationFactory::ForwardLocalError(struct IRestrictedErrorInfo *)   Unknown
    combase.dll!CallErrorForwarder(void * hProcess, int fLocal, IRestrictedErrorInfo * pRestrictedErrorInfo) Line 1167  C++
    msvcp140_app.dll!`Concurrency::details::_ExceptionHolder::ReportUnhandledError'::`1'::catch$3() Line 331    C++
    vcruntime140_app.dll!_CallSettingFrame()    Unknown
    vcruntime140_app.dll!__CxxCallCatchBlock()  Unknown
    ntdll.dll!RcConsolidateFrames() Unknown
    msvcp140_app.dll!Concurrency::details::_ExceptionHolder::ReportUnhandledError() Line 314    C++
    test-uwp.exe!Concurrency::details::_ExceptionHolder::~_ExceptionHolder() Line 750   C++
    test-uwp.exe!Concurrency::details::_Task_impl_base::~_Task_impl_base() Line 1483    C++
    test-uwp.exe!Concurrency::details::_Task_impl<unsigned char>::`scalar deleting destructor'(unsigned int)    C++
    test-uwp.exe!Concurrency::details::_PPLTaskHandle<unsigned char,Concurrency::task<unsigned char>::_InitialTaskHandle<void,void <lambda>(void),Concurrency::details::_TypeSelectorNoAsync>,Concurrency::details::_TaskProcHandle>::~_PPLTaskHandle<unsigned char,Concurrency::task<unsigned char>::_InitialTaskHandle<void,void <lambda>(void),Concurrency::details::_TypeSelectorNoAsync>,Concurrency::details::_TaskProcHandle>() Line 1406    C++
    test-uwp.exe!Concurrency::task<unsigned char>::_InitialTaskHandle<void,void <lambda>(void),Concurrency::details::_TypeSelectorNoAsync>::`scalar deleting destructor'(unsigned int)  C++
    test-uwp.exe!Concurrency::details::_DefaultPPLTaskScheduler::_PPLTaskChore::_Callback(void * _Args) Line 51 C++
    ntdll.dll!TppWorkpExecuteCallback() Unknown
    ntdll.dll!TppWorkerThread() Unknown
    kernel32.dll!BaseThreadInitThunk()  Unknown
    ntdll.dll!RtlUserThreadStart()  Unknown

Answer 1

a Working C++/CLI example

MySuperAppPage::MySuperAppPage(){
    // in main thread
    InitializeComponent();
    this->myTextBlock->Text = "mainThread"; // works

    Windows::UI::Core::CoreDispatcher^ dispatcher; //
    dispatcher = Windows::UI::Core::CoreWindow::GetForCurrentThread()->Dispatcher;

    create_task([this, dispatcher]() // async
    {
        while(true) {
            OutputDebugString(L"thread2\n"); // works
            dispatcher->RunAsync(Windows::UI::Core::CoreDispatcherPriority::Normal,
                                ref new Windows::UI::Core::DispatchedHandler(
            [this]()
            {
                this->myTextBlock->Text = "thread2"; // works
            }));
            Sleep(1000);
        }
    });
}