Question

我正在撰写 Windows Phone 8.1（WINRT XAML）应用。

在方法1中，我打开StorageFile ，而在方法2中，我正在写同一个文件。但它在写入文件时显示错误。

打开和阅读内容后如何关闭此文件？

然后如何在方法2中写入文件后再次关闭此文件？

private async Task<bool> Method1(int workOutID)
{
    string filename = "WorkoutOfflineDataFile.txt";
    StorageFolder LocalStorageFolderObject = ApplicationData.Current.LocalFolder;
    StorageFile StorageFileObject = await LocalStorageFolderObject.CreateFileAsync(filename, CreationCollisionOption.OpenIfExists);
    string JSONFromFile = await FileIO.ReadTextAsync(StorageFileObject);
}

private async void Method2()
{
    string filename = "WorkoutOfflineDataFile.txt";
    StorageFolder LocalStorageFolderObject = ApplicationData.Current.LocalFolder;
    StorageFile StorageFileObject = await LocalStorageFolderObject.CreateFileAsync(filename, CreationCollisionOption.OpenIfExists);
    await FileIO.WriteTextAsync(StorageFileObject, JSonData_ToSave);
}

ERROR：

抛出异常：＆＃39; System.UnauthorizedAccessException＆＃39;在   mscorlib.ni.dll

其他信息：访问被拒绝。（HRESULT的例外情况：   0x80070005（E_ACCESSDENIED））

Answer 1

代码看似正确，我认为异常是由别的东西引发的。

无论如何，如果您想确保在读/写操作后关闭文件和流，您可以使用一次性方式：

private async Task<bool> Method1(int workOutID)
{
    string filename = "WorkoutOfflineDataFile.txt";
    StorageFolder LocalStorageFolderObject = ApplicationData.Current.LocalFolder;
    StorageFile StorageFileObject = await LocalStorageFolderObject.CreateFileAsync(filename, CreationCollisionOption.OpenIfExists);
    using (var stream = await StorageFileObject.OpenStreamForReadAsync())
    {
        using (var reader = new StreamReader(stream))
        {
            string JSONFromFile = reader.ReadToEnd();
        }
    }
}

private async void Method2()
{
    string filename = "WorkoutOfflineDataFile.txt";
    StorageFolder LocalStorageFolderObject = ApplicationData.Current.LocalFolder;
    StorageFile StorageFileObject = await LocalStorageFolderObject.CreateFileAsync(filename, CreationCollisionOption.OpenIfExists);
    using (var stream = await StorageFileObject.OpenStreamForWriteAsync())
    {
        using (var writer = new StreamWriter(stream))
        {
            writer.Write(JSonData_ToSave);
        }
    }
}

Answer 2

Festyk的解决方案是否有效？也许只是尝试使用：

StorageFile StorageFileObject = await LocalStorageFolderObject.GetFileAsync(filename);

在你的第二种方法中，如果你确定文件已经存在 - 请记住，否则会引发异常。

Answer 3

您正在使用method1（）

锁定文件

private async Task<bool> Method1(int workOutID)
{
    string filename = "WorkoutOfflineDataFile.txt";
    StorageFolder LocalStorageFolderObject = ApplicationData.Current.LocalFolder;
    StorageFile StorageFileObject = await LocalStorageFolderObject.CreateFileAsync(filename, CreationCollisionOption.OpenIfExists);
    string JSONFromFile = await FileIO.ReadTextAsync(StorageFileObject);
}

当您尝试访问WorkoutOfflineDataFile.txt时，您实际上是在锁定此文件，因此在关闭之前没有其他线程可以触摸它。

卢卡的回答似乎是好的和安全的。尝试使用它。

如何关闭打开的StorageFile？

3 个答案: