System.InvalidCast exception Windows Runtime

Question

I am building an ebook manager for the windows store and I have implemented the IUriToStreamResolver Interface on one of my classes. I am using that to open an epub. The code is as follows:

public IAsyncOperation<IInputStream> UriToStreamAsync(Uri uri)
{
     if(uri == null)
     {
         throw new Exception();
     }

     string path = uri.AbsolutePath;

     return GetContent(path).AsAsyncOperation();
}


private async Task<IInputStream> GetContent(string path)
{
     path = path.TrimStart('/');
     var file = await StorageApplicationPermissions.FutureAccessList.GetFileAsync(App.token);
     var stream = await file.OpenAsync(FileAccessMode.Read);
     var archive = new ZipArchive(stream.AsStream());
     var entry = archive.Entries.Where(a => a.FullName == path);
     var entryStream = entry.First().Open();
     return entryStream.AsInputStream();
}

After returning from the GetContent() method I get a cryptic System.InvalidCast exception. I enabled mixed debugging thinking I could get a little more information but it is not very helpful.

Here is the stack:

combase.dll!RoFailFastWithErrorContextInternal(long,unsigned long,struct _STOWED_EXCEPTION_INFORMATION_V1 * * const) Unknown combase.dll!_RoFailFastWithErrorContext@4() 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 *,int,struct IRestrictedErrorInfo *) Unknown combase.dll!_RoReportUnhandledError@4() Unknown mscorlib.ni.dll!63eb2d62() Unknown [Frames below may be incorrect and/or missing, no symbols loaded for mscorlib.ni.dll]
[Managed to Native Transition]
mscorlib.dll!System.Runtime.InteropServices.WindowsRuntime.WindowsRuntimeMarshal.RoReportUnhandledError(System.Runtime.InteropServices.WindowsRuntime.IRestrictedErrorInfo error) Unknown mscorlib.dll!System.Runtime.InteropServices.WindowsRuntime.WindowsRuntimeMarshal.ReportUnhandledError(System.Exception e) Unknown System.Runtime.WindowsRuntime.dll!System.Threading.WinRTSynchronizationContext.Invoker.InvokeCore() Unknown System.Runtime.WindowsRuntime.dll!System.Threading.WinRTSynchronizationContext.Invoker.InvokeInContext(object thisObj) Unknown mscorlib.dll!System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Unknown mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Unknown System.Runtime.WindowsRuntime.dll!System.Threading.WinRTSynchronizationContext.Invoker.Invoke() Unknown [Native to Managed Transition]
Windows.UI.dll!Windows::UI::Core::CDispatcher::ProcessInvokeItem() Line 794 C++ Windows.UI.dll!Windows::UI::Core::CDispatcher::WaitAndProcessMessages(void * hEventWait) C++ Windows.UI.dll!Windows::UI::Core::CDispatcher::ProcessEvents(Windows::UI::Core::CoreProcessEventsOption options=CoreProcessEventsOption_ProcessUntilQuit) Line 390 C++ Windows.UI.Xaml.dll!DirectUI::FrameworkView::Run() Unknown twinapi.appcore.dll!Windows::ApplicationModel::Core::CoreApplicationView::Run(void) Unknown twinapi.appcore.dll!Windows::Foundation::Collections::Internal::HashMap,struct Windows::Foundation::Collections::Internal::DefaultEqualityPredicate,struct Windows::Foundation::Collections::Internal::DefaultLifetimeTraits,struct Windows::ApplicationModel::Core::Details::SmugglableInterfaceLifetimeTraits,struct Windows::Foundation::Collections::Internal::HashMapOptions,0,1,0> >::Remove(unsigned int) Unknown SHCore.dll!Microsoft::WRL::RuntimeClass,class CScalingInfoBase,struct ICurrentWindowChangeListener,class Microsoft::WRL::FtmBase,class Microsoft::WRL::Details::Nil,class Microsoft::WRL::Details::Nil,class Microsoft::WRL::Details::Nil,class Microsoft::WRL::Details::Nil,class Microsoft::WRL::Details::Nil,class Microsoft::WRL::Details::Nil>::`vector deleting destructor'(unsigned int) Unknown kernel32.dll!@BaseThreadInitThunk@12() Unknown ntdll.dll!__RtlUserThreadStart() Unknown ntdll.dll!__RtlUserThreadStart@8() Unknown

And here is the only local: $exceptionstack

    [9 Frames, combase.dll!_RoOriginateLanguageException@12()] 
    [0] combase.dll!_RoOriginateLanguageException@12() void*
    [1] mscorlib.ni.dll!63eb2c8a()  void*
    [2] mscorlib.ni.dll!63f4ffa2()  void*
    [3] mscorlib.ni.dll!63f4fd61()  void*
    [4] System.Runtime.WindowsRuntime.ni.dll!506ef9df() void*
    [5] System.Runtime.WindowsRuntime.ni.dll!506ef965() void*
    [6] mscorlib.ni.dll!63823156()  void*
    [7] System.Runtime.WindowsRuntime.ni.dll!506ef934() void*
    [8] Windows.UI.ni.dll!50e1ff16()    void*

Any help or direction is much appreciated!

Answer 1

I fixed it but I am not sure it is the optimal solution. If anyone would like to suggest improvements I am game.

In my GetContent() method I made the following changes:

private async Task<IInputStream> GetContent(string path)
    {
        try
        {
            path = path.TrimStart('/');
            var file = await StorageApplicationPermissions.FutureAccessList.GetFileAsyn(App.token);

            var archive = new ZipArchive(await file.OpenStreamForReadAsync(),ZipArchiveMode.Read);
            var entry = archive.GetEntry(path);
            var contents = new byte[entry.Length];
            var entryStream = entry.Open();
            var tempFile = await ApplicationData.Current.LocalFolder.CreateFileAsync("temp.xhtml",CreationCollisionOption.ReplaceExisting);
            var decompressedStream = await tempFile.OpenStreamForWriteAsync();
            await entryStream.CopyToAsync(decompressedStream, (int)entry.Length);
            await decompressedStream.FlushAsync();
            decompressedStream.Dispose();
            var returnFile = await ApplicationData.Current.LocalFolder.GetFileAsync("temp.xhtml");
            var returnStream = await returnFile.OpenSequentialReadAsync();
            return returnStream;
        }
        catch (Exception e)
        {

            throw;
        }
    }