UnauthorizedAccessException使用FileOpenPicker

Question

时，我有一个CommandBar在我的Windows应用商店的应用程序，当我点击我的CommandBar的Open按钮，它如下运行OpenFile处理程序：

private async void OpenFile(object sender, RoutedEventArgs e) 
{ 
    MessageDialog dialog = new MessageDialog("You are about to open a new file. Do you want to save your work first?"); 
    dialog.Commands.Add(new UICommand("Yes", new UICommandInvokedHandler(SaveAndOpen))); 
    dialog.Commands.Add(new UICommand("No", new UICommandInvokedHandler(Open))); 
    await dialog.ShowAsync(); 
} 

private async void SaveAndOpen(IUICommand command) 
{ 
    await SaveFile(); 
    Open(command); 
} 

private async void Open(IUICommand command) 
{ 
    FileOpenPicker fileOpenPicker = new FileOpenPicker(); 
    fileOpenPicker.ViewMode = PickerViewMode.List; 
    fileOpenPicker.FileTypeFilter.Add(".txt"); 
    StorageFile file = await fileOpenPicker.PickSingleFileAsync(); 
    await LoadFile(file); 
} 

我看到消息就好了，但只有当我点击Yes时才会收到FileOpenPicker。当我打No我得到一个UnauthorizedAccessException: Access is denied.在下面一行：StorageFile file = await fileOpenPicker.PickSingleFileAsync();

我百思不得其解......没有人知道为什么会这样？我甚至尝试运行它在截止机会，处理程序被调用在不同的线程调度器，但是...不幸的是，同样的事情：

await CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(CoreDispatcherPriority.High, async() => 
{ 
    StorageFile file = await fileOpenPicker.PickSingleFileAsync(); 
    await LoadFile(file); 
}); 

Answer 1

是，它RT的对话框竞争条件是由于。解决的办法是让我字面上利用MessageDialog类以同样的方式，你会用MessageBox.Show在WinForms：

private async void OpenFile(object sender, RoutedEventArgs e) 
{ 
    MessageDialog dialog = new MessageDialog("You are about to open a new file. Do you want to save your work first?"); 
    IUICommand result = null; 
    dialog.Commands.Add(new UICommand("Yes", (x) => 
    { 
     result = x; 
    })); 
    dialog.Commands.Add(new UICommand("No", (x) => 
    { 
     result = x; 
    })); 
    await dialog.ShowAsync(); 
    if (result.Label == "Yes") 
    { 
     await SaveFile(); 
    } 
    FileOpenPicker fileOpenPicker = new FileOpenPicker(); 
    fileOpenPicker.ViewMode = PickerViewMode.List; 
    fileOpenPicker.FileTypeFilter.Add(".txt"); 
    StorageFile file = await fileOpenPicker.PickSingleFileAsync(); 
    await LoadFile(file); 
}