C++/CX - DataReader out of bounds exception - c++

Question

I have the following code which opens a file and it works most of the time for one time. After that I get exceptions thrown and I don't know where the problem is hiding. I tried to look for this for a couple of days already but no luck.
String^ xmlFile = "Assets\\TheXmlFile.xml";
xml = ref new XmlDocument();
StorageFolder^ InstallationFolder = Windows::ApplicationModel::Package::Current->InstalledLocation;
task<StorageFile^>(
InstallationFolder->GetFileAsync(xmlFile)).then([this](StorageFile^ file) {
if (nullptr != file) {
task<Streams::IRandomAccessStream^>(file->OpenAsync(FileAccessMode::Read)).then([this](Streams::IRandomAccessStream^ stream)
{
IInputStream^ deInputStream = stream->GetInputStreamAt(0);
DataReader^ reader = ref new DataReader(deInputStream);
reader->InputStreamOptions = InputStreamOptions::Partial;
reader->LoadAsync(stream->Size);
strXml = reader->ReadString(stream->Size);
MessageDialog^ dlg = ref new MessageDialog(strXml);
dlg->ShowAsync();
});
}
});
The error is triggered at this part of the code:
strXml = reader->ReadString(stream->Size);
I get the following error:
First-chance exception at 0x751F5B68 in XmlProject.exe: Microsoft C++ exception: Platform::OutOfBoundsException ^ at memory location 0x02FCD634. HRESULT:0x8000000B The operation attempted to access data outside the valid range
WinRT information: The operation attempted to access data outside the valid range
Just like I said, the first time it just works but after that I get the error. I tried detaching the stream and buffer of the datareader and tried to flush the stream but no results.

Answer 1

I've also asked this question on the Microsoft C++ forums and credits to the user "Viorel_" I managed to get it working. Viorel said the following:
Since LoadAsync does not perform the operation immediately, you should probably add a corresponding “.then”. See some code: https://social.msdn.microsoft.com/Forums/windowsapps/en-US/94fa9636-5cc7-4089-8dcf-7aa8465b8047. This sample uses “create_task” and “then”: https://code.msdn.microsoft.com/vstudio/StreamSocket-Sample-8c573931/sourcecode (file Scenario1.xaml.cpp, for example).
I have had to separate the content in the task<Streams::IRandomAccessStream^> and split it up in separate tasks.
I reconstructed my code and I have now the following:
String^ xmlFile = "Assets\\TheXmlFile.xml";
xml = ref new XmlDocument();
StorageFolder^ InstallationFolder = Windows::ApplicationModel::Package::Current->InstalledLocation;
task<StorageFile^>(
InstallationFolder->GetFileAsync(xmlFile)).then([this](StorageFile^ file) {
if (nullptr != file) {
task<Streams::IRandomAccessStream^>(file->OpenAsync(FileAccessMode::Read)).then([this](Streams::IRandomAccessStream^ stream)
{
IInputStream^ deInputStream = stream->GetInputStreamAt(0);
DataReader^ reader = ref new DataReader(deInputStream);
reader->InputStreamOptions = InputStreamOptions::Partial;
create_task(reader->LoadAsync(stream->Size)).then([reader, stream](unsigned int size){
strXml = reader->ReadString(stream->Size);
MessageDialog^ dlg = ref new MessageDialog(strXml);
dlg->ShowAsync();
});
});
}
});