How Can I Avoid Crashing on Pressing Backbutton?

Question

Customized hardware backbutton crashed in C++, but OK in C#:
//in the constructor
Windows::Phone::UI::Input::HardwareButtons::BackPressed += ref new Windows::Foundation::EventHandler<Windows::Phone::UI::Input::BackPressedEventArgs ^>(this, &AppExit::MainPage::OnBackPressed);
//Handler
void AppExit::MainPage::OnBackPressed(Object^ sender, Windows::Phone::UI::Input::BackPressedEventArgs^ e)
Windows::UI::Xaml::Controls::Frame^ frame = safe_cast<Windows::UI::Xaml::Controls::Frame^> (Window::Current->Content);
if (frame == nullptr)
return;
if (frame->CanGoBack)
frame->GoBack();
e->Handled = true;
Exception:
First-chance exception at 0x77AD210B in AppExit.exe: Microsoft C++ exception: Platform::DisconnectedException ^ at memory location 0x0124ECCC. HRESULT:0x80010108 The object invoked has disconnected from its clients.
WinRT information: The object invoked has disconnected from its clients.
Stack trace:
[External Code]
CoreUIComponents.dll!767de357()
CoreUIComponents.dll!767dd6b5()
CoreUIComponents.dll!767da92d()
CoreUIComponents.dll!7678c446()
CoreUIComponents.dll!767626f4()
CoreUIComponents.dll!767d2443()
CoreUIComponents.dll!767b735b()
CoreUIComponents.dll!767ae183()
CoreUIComponents.dll!767acd00()
CoreUIComponents.dll!767a752c()
CoreUIComponents.dll!767ab703()
CoreUIComponents.dll!7679dfc5()
CoreUIComponents.dll!7676576f()
[External Code]
But it works well in C#:
//constructor
Windows.Phone.UI.Input.HardwareButtons.BackPressed += HardwareButtons_BackPressed;
//handler
private void HardwareButtons_BackPressed(object sender, Windows.Phone.UI.Input.BackPressedEventArgs e)
Frame frame = Window.Current.Content as Frame;
if (frame == null)
return;
if (frame.CanGoBack)
frame.GoBack();
e.Handled = true;
Can I avoid this crash?

Answer 1

Hi Sal,
I've tested it and I can see the first-chance exception thrown, but the error message does not look same:
First-chance exception at 0x77776FB2 in App44.exe: Microsoft C++ exception: Cn::XH at memory location 0x018AF218.
First-chance exception at 0x77776FB2 in App44.exe: Microsoft C++ exception: Cn::XH at memory location 0x018AE350.
First-chance exception at 0x77776FB2 in App44.exe: Microsoft C++ exception: Cn::XH at memory location 0x018AE350.
First-chance exception at 0x77776FB2 in App44.exe: Microsoft C++ exception: Cn::XH at memory location 0x018AE350.
Actually we don't need to care about first chance exception, here is a blog:
http://blogs.msdn.com/b/davidklinems/archive/2005/07/12/438061.aspx even its long time ago but still helpful:
Does a first chance exception mean there is a problem in my code?
First chance exception messages most often do not mean there is a problem in the code. For applications / components which handle exceptions gracefully, first chance exception messages let the developer know that an exceptional situation was encountered
and was handled.
--James
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