vb.net – WinRT – 访问被拒绝读取文件

我是否必须在清单中声明我要在LocalStorage中保存文件？我知道我必须为我的文件,或者我错过了什么？这是我的示例方法,说明了我如何写出文件：

''' <summary>
    ''' Writes all of the text to the specified file in one of the specified safe storage folders.
    ''' </summary>
    ''' <param name="text">The text to write.</param>
    ''' <param name="append">Whether or not to append the data or overwrite what is in the file.</param>
    ''' <param name="fileName">The name of the file to write the data to.</param>
    ''' <param name="safeFolder">The safe storage folder that should be written to.  These folders are isolated for the application to use
    ''' and do not require additional manifest permissions.</param>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Public Shared Async Function WriteAllText(text As String,append As Boolean,fileName As String,safeFolder As SafeStorageFolder) As Task
        Dim folder As Windows.Storage.StorageFolder

        Select Case safeFolder
            Case SafeStorageFolder.Local
                folder = Windows.Storage.ApplicationData.Current.LocalFolder
            Case SafeStorageFolder.Roaming
                folder = Windows.Storage.ApplicationData.Current.RoamingFolder
            Case SafeStorageFolder.Temp
                folder = Windows.Storage.ApplicationData.Current.TemporaryFolder
            Case Else
                folder = Windows.Storage.ApplicationData.Current.LocalFolder
        End Select

        Dim sf As StorageFile

        If append = True Then
            sf = Await folder.CreateFileAsync(fileName,Windows.Storage.CreationCollisionOption.OpenIfExists)
        Else
            sf = Await folder.CreateFileAsync(fileName,Windows.Storage.CreationCollisionOption.ReplaceExisting)
        End If

        ' WriteTextAsync will always overwrite the file even if the existing file has been opened.  We'll use
        ' AppendTextAsync here,the above CreateFileAsync will handle whether the file has been truncated or not.
        Await FileIO.AppendTextAsync(sf,text)

    End Function