UnauthorizedAccessException使用FileOpenPicker

Question

時，我有一個CommandBar在我的Windows應用商店的應用程序，當我點擊我的CommandBar的Open按鈕，它如下運行OpenFile處理程序：

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，但只有當我點擊Yes時纔會收到FileOpenPicker。當我打No我得到一個UnauthorizedAccessException: Access is denied.在下面一行：StorageFile file = await fileOpenPicker.PickSingleFileAsync();

我百思不得其解......沒有人知道爲什麼會這樣？我甚至嘗試運行它在截止機會，處理程序被調用在不同的線程調度器，但是...不幸的是，同樣的事情：

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

Answer 1

是，它RT的對話框競爭條件是由於。解決的辦法是讓我字面上利用MessageDialog類以同樣的方式，你會用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); 
}