C++/CX - DataReader超出范围例外

Question

我有以下代码可以打开一个文件，并且它大部分时间都可以运行一次。之后，我得到异常抛出，我不知道问题隐藏在哪里。我已经尝试了几天，但没有运气。

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();  
     }); 
    } 
}); 

错误触发在这部分代码：

strXml = reader->ReadString(stream->Size); 

我收到以下错误：

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的信息：操作试图超出了有效访问数据范围

就像我说的，它第一次正常工作，但之后，我得到了呃ROR。我尝试分离datareader的流和缓冲区，并试图刷新流，但没有结果。

Answer 1

我也在Microsoft C++论坛上问过这个问题，并在user“Viorel_”上写道，我设法让它工作。维奥雷尔下面说：

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).

我不得不在task<Streams::IRandomAccessStream^>内容分开和独立的任务分裂它。

我重建我的代码，我现在有以下几点：

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(); 
      });    
     }); 
    } 
});