MvvmCross: NotImplementedException calling EnsureFolderExists method of IMvxFileStore - windows-store-apps

Question

I'm developing my first Windows Store App, using MvvmCross framework and I have a problem with images management. In particular I have the following simple ViewModel in my PCL project, and a Store project with a button bound with AddPictureCommand.
public class FirstViewModel : MvxViewModel
{
IMvxPictureChooserTask _pictureChooserTask;
IMvxFileStore _fileStore;
public FirstViewModel(IMvxPictureChooserTask pictureChooserTask, IMvxFileStore fileStore)
{
_pictureChooserTask = pictureChooserTask;
_fileStore = fileStore;
}
private byte[] _pictureBytes;
public byte[] PictureBytes
{
get { return _pictureBytes; }
set
{
if (_pictureBytes == value) return;
_pictureBytes = value;
RaisePropertyChanged(() => PictureBytes);
}
}
public ICommand AddPictureCommand
{
get { return new MvxCommand(() =>
{
_pictureChooserTask.ChoosePictureFromLibrary(400, 95, pictureAvailable, () => { });
}); }
}
private void pictureAvailable(Stream stream)
{
MemoryStream memoryStream = new MemoryStream();
stream.CopyTo(memoryStream);
PictureBytes = memoryStream.ToArray();
GenerateImagePath();
}
private string GenerateImagePath()
{
if (PictureBytes == null) return null;
var RandomFileName = "Image" + Guid.NewGuid().ToString("N") + ".jpg";
_fileStore.EnsureFolderExists("Images");
var path = _fileStore.PathCombine("Images", RandomFileName);
_fileStore.WriteFile(path, PictureBytes);
return path;
}
}
The problem is that the method _fileStore.EnsureFolderExists("Images");
gives me the an "NotImplementedException" with message: "Need to implement this - doesn't seem obvious from the StorageFolder API".
Has anyone already seen it before?
Thank you

Answer 1

This not implemented exception is documented in the wiki - see https://github.com/MvvmCross/MvvmCross/wiki/MvvmCross-plugins#File
It should be fairly straightforward to implement these missing methods if they are required. Indeed I know of at least 2 users that have implemented these - but sadly they've not contributed them back.
to implement them, just
fork (copy) the code from https://github.com/MvvmCross/MvvmCross/blob/v3/Plugins/Cirrious/File/Cirrious.MvvmCross.Plugins.File.WindowsStore/MvxWindowsStoreBlockingFileStore.cs
implement the missing methods using the winrt StorageFolder apis
in your Store UI project, don't load the File plugin - so comment out or remove the File bootstrap class.
during setup, register your implementation with ioc using Mvx.RegisterType - e.g.:
protected override void InitializeFirstChance()
{
base.InitializeFirstChance();
Cirrious.CrossCore.Mvx.RegisterType<IMvxFileStore, MyFileStore>();
}
For more on using ioc, see https://github.com/MvvmCross/MvvmCross/wiki/Service-Location-and-Inversion-of-Control
For more on customising the setup sequence, see https://github.com/MvvmCross/MvvmCross/wiki/Customising-using-App-and-Setup

Answer 2

Following Stuart's suggestions I've implemented the following methods for Windows 8 Store App:
public bool FolderExists(string folderPath)
{
try
{
var directory = ToFullPath(folderPath);
var storageFolder = StorageFolder.GetFolderFromPathAsync(directory).Await();
}
catch (FileNotFoundException)
{
return false;
}
catch (Exception ex)
{
MvxTrace.Trace("Exception in FolderExists - folderPath: {0} - {1}", folderPath, ex.ToLongString());
throw ex;
}
return true;
//throw new NotImplementedException("Need to implement this - See EnsureFolderExists");
}
public void EnsureFolderExists(string folderPath)
{
try
{
var directory = ToFullPath(folderPath);
var storageFolder = StorageFolder.GetFolderFromPathAsync(directory).Await();
}
catch (FileNotFoundException)
{
var localFolder = ToFullPath(string.Empty);
var storageFolder = StorageFolder.GetFolderFromPathAsync(localFolder).Await();
storageFolder.CreateFolderAsync(folderPath).Await();
}
catch (Exception ex)
{
MvxTrace.Trace("Exception in EnsureFolderExists - folderPath: {0} - {1}", folderPath, ex.ToLongString());
throw ex;
}
//throw new NotImplementedException("Need to implement this - doesn't seem obvious from the StorageFolder API");
//var folder = StorageFolder.GetFolderFromPathAsync(ToFullPath(folderPath)).Await();
}
The third method we need to implement is DeleteFolder(string folderPath, bool recursive). Unfortunately StorageFolder method "DeleteFolder" doesn't have a "recursive" parameter. So I should implement DeleteFolder ignoring it:
public void DeleteFolder(string folderPath, bool recursive)
{
try
{
var directory = ToFullPath(folderPath);
var storageFolder = StorageFolder.GetFolderFromPathAsync(directory).Await();
storageFolder.DeleteAsync().Await();
}
catch (FileNotFoundException)
{
//Folder doesn't exist. Nothing to do
}
catch (Exception ex)
{
MvxTrace.Trace("Exception in DeleteFolder - folderPath: {0} - {1}", folderPath, ex.ToLongString());
throw ex;
}
//throw new NotImplementedException("Need to implement this - See EnsureFolderExists");
}
or I should check if the folder is empty before to delete it if "recursive" equals false.
Better implementations are welcomed.