StorageFile::GetFileFromPathAsync does not work

Question

Hi all, I try to get file to process in Metro. I use the following code to do, but code run to auto fileOp = StorageFile::GetFileFromPathAsync("D:\\test\\a.docx"); the app hang. Anybody know how to get a StorageFile object from a absolute path?

 

auto fileOp = StorageFile::GetFileFromPathAsync("D:\\test\\a.docx");

fileOp->Completed = ref new AsyncOperationCompletedHandler<StorageFile ^>([=]IAsyncOperation<StorageFile^>^ a)

{

});

fileOp->Start();

 

In VS2001 output window, I can see a exception occured: Microsoft C++ exception: Platform::AccessDeniedException ^ at memory location 0x029CE81C. It looks like need some permission to access external file. But while i try to use FilePicker class to select D:\test\a.docx, it can return a normal StorageFile object, why?

Answer 1

The picker allows access because the user provided the file to you.  Also, they provided the file, not the path.  Basically your application using the FilePicker now has access to the stream, not directly to the path.  If you set the Documents capability in the manifest then you can programmatically access files that are in the user's Documents folders but not any arbitrary path.

---

Tim Heuer | Program Manager, XAML | http://timheuer.com/blog | @timheuer

(if my post has answered your question, please consider using the 'mark as answer' feature in the forums to help others)

Answer 2

You can also access your application's temp folder.  See the following thread for an example of that:

http://social.msdn.microsoft.com/Forums/en-US/wingameswithdirectx/thread/f5f8dbce-f318-4de3-9e7d-55ed1a04dad1

Raman

Answer 3

Is it possible to open this limitation in future by MS?

Answer 4

I appreciate your feedback in this area! Do you have a particular scenario where the available avenues for accessing files in a Metro style app are not sufficient for your application?

This particular ask on the surface conflicts with the vision of Metro style apps, as Tim put it, having direct access to an arbitrary folder outside of the  Windows.Storage.ApplicationData.Current folders since a Metro style app should not be dependent upon a users drive / folder layout or have the ability to manipulate it outside of what was mentioned above.

-David

Answer 5

Suppose I want to process 100 files from a USB drive directory.

It would be too painful to ask the user to select each one.  Why can't the user, at runtime, grant the application the ability to read from or write to any directory (and child directories) they want?

Will Metro force the user to be instructed to use Explorer to copy those files to an application directory? 

 

 

 

Answer 6

I appreciate your feedback in this area! Do you have a particular scenario where the available avenues for accessing files in a Metro style app are not sufficient for your application?

This particular ask on the surface conflicts with the vision of Metro style apps, as Tim put it, having direct access to an arbitrary folder outside of the  Windows.Storage.ApplicationData.Current folders since a Metro style app should not be dependent upon a users drive / folder layout or have the ability to manipulate it outside of what was mentioned above.

-David

We want to search the whole computer's files and category them. Maybe it is better to add a capability "Access Computer's file system" just like Android did(SD Card permission).

Answer 7

The picker allows access because the user provided the file to you.  Also, they provided the file, not the path.  Basically your application using the FilePicker now has access to the stream, not directly to the path.  If you set the Documents capability in the manifest then you can programmatically access files that are in the user's Documents folders but not any arbitrary path.

---

Tim Heuer | Program Manager, XAML | http://timheuer.com/blog | @timheuer

(if my post has answered your question, please consider using the 'mark as answer' feature in the forums to help others)

Thanks, Tim. We will re-design our product.

Answer 8

Suppose I want to build a metro style version of Winamp. How am I supposed to read each file of a playlist of audio files?

Answer 9

You cant access  that sort of directory from Metro.

It has to be one of the folders in the app manifest and has to be declared in the manifest too.

Beware though. the temp folder files are destroyed when Win 8 closes down.

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n.Wright

Answer 10

You can use the FolderPicker to let the user explicitly identify a folder. You then have access to any file in the folder or any of its subfolders.