UWP UnauthorizedException

我目前正在编写我的第一个UWP应用程序，只是为了了解情况。我正在构建一个小应用程序，从下载的facebook存档中提取数据。

但是当我尝试打开文件时(即使每个人都有完全访问权限)，我得到一个UnauthorizedException。我不明白这一点，我还没有发现任何人在任何旧文件上都有这个问题(有很多人在更具体的情况下有问题，但不仅仅是他们硬盘上的一个简单文件)

System.UnauthorizedAccessException was unhandled by user code
  HResult=-2147024891
  Message=Access to the path 'C:'Users'patri'Downloads'facebook-100004420950389'html'messages.htm' is denied.
  Source=System.IO.FileSystem
  StackTrace:
       at System.IO.WinRTIOExtensions.<TranslateWinRTTaskCore>d__1`1.MoveNext()
    --- End of stack trace from previous location where exception was thrown ---
       at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
       at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
       at System.IO.WinRTFileSystem.<OpenAsync>d__1.MoveNext()
    --- End of stack trace from previous location where exception was thrown ---
       at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
       at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
       at System.IO.WinRTFileSystem.Open(String fullPath, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options, FileStream parent)
       at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options)
       at System.Xml.XmlSystemPathResolver.GetEntity(Uri uri, String role, Type typeOfObjectToReturn)
       at System.Xml.XmlTextReaderImpl.FinishInitUriString()
       at System.Xml.XmlReaderSettings.CreateReader(String inputUri, XmlParserContext inputContext)
       at System.Xml.Linq.XDocument.Load(String uri, LoadOptions options)
       at Facebookalyzer.FacebookArchiveParser.PopulateArchiveFromHtml(String filePath, FacebookMessageArchive archive)
       at Facebookalyzer.FacebookArchiveParser.<>c__DisplayClass0_0.<ExtractAllChatMessages>b__0()
       at System.Threading.Tasks.Task.Execute()
  InnerException:

有人知道为什么我得到这个异常吗?或者它只是一个事实，你不应该在UWP-Apps中直接访问硬盘上的文件(这会让我质疑为什么他们提供一个文件打开对话框，如果是这样的话)