win8学习--------File

//创建文件
using namespace Windows::Storage; 
MainPage^ rootPage;
 rootPage = MainPage::Current;
create_task(KnownFolders::DocumentsLibrary->CreateFileAsync(rootPage->Filename, CreationCollisionOption::ReplaceExisting)).then([this](StorageFile^ file)
    {
        rootPage->SampleFile = file;
        OutputTextBlock->Text = "The file '" + file->Name + "' was created.";
    });

static property Platform::String^ Filename
{
Platform::String^ get()
{
return ref new Platform::String(L"sample.dat");
}
}

property Windows::Storage::StorageFile^ SampleFile
{
Windows::Storage::StorageFile^ get()
{
return sampleFile;
}
void set(Windows::Storage::StorageFile^ value)
{
sampleFile = value;
}
}

2、向文件中写入信息----写Text内容
//另加空间名using namespace concurrency;
StorageFile^ file = rootPage->SampleFile;//刚才创建的文件
    if (file != nullptr)
    {
        String^ userContent = InputTextBox->Text;
        if (userContent != nullptr && !userContent->IsEmpty())
        {
            create_task(FileIO::WriteTextAsync(file, userContent)).then([this, file, userContent](task<void> task)
            {
                try
                {
                    task.get();
                    OutputTextBlock->Text = "The following text was written to '" + file->Name + "':\n\n" + userContent;
                }
                catch(COMException^ ex)
                {
                    rootPage->HandleFileNotFoundException(ex);
                }
            });
        }
        else
        {
            OutputTextBlock->Text = "The text box is empty, please write something and then click 'Write' again.";
        }
    }

//读文件内容-----读text内容

 rootPage->ResetScenarioOutput(OutputTextBlock);
    StorageFile^ file = rootPage->SampleFile;
    if (file != nullptr)
    {
        String^ userContent = InputTextBox->Text;
        if (userContent != nullptr && !userContent->IsEmpty())
        {
            IBuffer^ buffer = GetBufferFromString(userContent);
            create_task(FileIO::WriteBufferAsync(file, buffer)).then([this, file, buffer, userContent](task<void> task)
            {
                try
                {
                    task.get();
                    OutputTextBlock->Text = "The following " + buffer->Length.ToString() + " bytes of text were written to '" + file->Name + "':\n\n" + userContent;
                }
                catch(COMException^ ex)
                {
                    rootPage->HandleFileNotFoundException(ex);
                }
            });
        }
        else
        {
            OutputTextBlock->Text = "The text box is empty, please write something and then click 'Write' again.";
        }
    }

 

//写Byte流
using namespace Windows::Storage::Streams;
 rootPage->ResetScenarioOutput(OutputTextBlock);
    StorageFile^ file = rootPage->SampleFile;
    if (file != nullptr)
    {
        String^ userContent = InputTextBox->Text;
        if (userContent != nullptr && !userContent->IsEmpty())
        {
            create_task(file->OpenTransactedWriteAsync()).then([this, file, userContent](task<StorageStreamTransaction^> task)
            {
                try
                {
                    StorageStreamTransaction^ transaction = task.get();
                    DataWriter^ dataWriter = ref new DataWriter(transaction->Stream);
                    dataWriter->WriteString(userContent);
                    create_task(dataWriter->StoreAsync()).then([this, file, dataWriter, transaction, userContent](unsigned int bytesWritten)
                    {
                        transaction->Stream->Size = bytesWritten; // reset stream size to override the file
                        create_task(transaction->CommitAsync()).then([this, file, userContent]()
                        {
                            OutputTextBlock->Text = "The following text was written to '" + file->Name + "' using a stream:\n\n" + userContent;
                        });
                    });
                }
                catch(COMException^ ex)
                {
                    rootPage->HandleFileNotFoundException(ex);
                }
            });
        }
        else
        {
            OutputTextBlock->Text = "The text box is empty, please write something and then click 'Write' again.";
        }
    }

//读byte流

rootPage->ResetScenarioOutput(OutputTextBlock);
StorageFile^ file = rootPage->SampleFile;
if (file != nullptr)
{
create_task(FileIO::ReadBufferAsync(file)).then([this, file](task<IBuffer^> task)
{
try
{
IBuffer^ buffer = task.get();
DataReader^ dataReader = DataReader::FromBuffer(buffer);
String^ fileContent = dataReader->ReadString(buffer->Length);
OutputTextBlock->Text = "The following " + buffer->Length.ToString() + " bytes of text were read from '" + file->Name + "':\n\n" + fileContent;
}
catch(COMException^ ex)
{
rootPage->HandleFileNotFoundException(ex);
}
});
}