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public List<string> Uris;

private ObservableCollection<MediaFile> _images;
public  ObservableCollection<MediaFile> Images {
    get { return _images ?? (_images = new ObservableCollection< MediaFile >()); }
    set {
        if(_images != value) {
            _images = value;
            OnPropertyChanged();
        }
    }
}

/// <summary>
/// Allows the user to pick a photo on their device using the native photo handlers and returns a stream, which we save to disk.
/// </summary>
/// <returns>string, the name of the image if everything went ok, 'false' if an exception was generated, and 'notfalse' if they simply canceled.</returns>
public async Task<string> PickPictureAsync() {

    MediaFile file      = null;
    string    filePath  = string.Empty;
    string    imageName = string.Empty;

    try {
        file = await CrossMedia.Current.PickPhotoAsync();

        #region Null Check

         if(file == null) { return null; }                                                                                 //Not returning false here so we do not show an error if they simply hit cancel from the device's image picker

        #endregion

        imageName = "SomeImageName.jpg";
        filePath  = /* Add your own logic here for where to save the file */ //_fileHelper.CopyFile(file.Path, imageName);
    } catch(Exception ex) {
         Debug.WriteLine("\nIn PictureViewModel.PickPictureAsync() - Exception:\n{0}\n", ex);                           //TODO: Do something more useful
         return null;
    } finally { if(file != null) { file.Dispose(); } }

    Receipts.Add(ImageSource.FromFile(filePath));

    Uris.Add(filePath);

    return imageName;
}

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