如何将某些项设置为LongListMultiSelector之前选择的某些项

Question

I am using wpToolkit's LongListMultiSelector.

I want to select different songs from different albums.

1. First go to "Album 1" page select "song 1", "song 2".
2. Came back to album List page.
3. Again go to same album "Album 1" page.

I want to show user that "song 1", "song 2" are selected before try to select one. But I am unable to mark the previous selected songs, if user came back to the same album.

Is there any way to do that.

Answer 1

Check the selected SongList with the album songs. then add to the lls like that.

llms.ItemsSource = this.mediaCollection;

int i = 0;
foreach (StorageFile file in SongList) //SongList of the album
{
    var thumb = await GetThumbImage(file, ThumbnailMode.MusicView, 150);

    var songItem = new songModel() { StorageFile = file, ThumbImage = thumb };//songModel is a song class
    this.mediaCollection.Add(songItem); 

    if (MultiplePhoto.Instance.SongItems.Count > 0) //SongItems contains the selected songlist
       if (MultiplePhoto.Instance.SongItems.FirstOrDefault(x => x.StorageFile.Path == songItem.StorageFile.Path) != null) // check that is currently added song selected?
          llms.SelectedItems.Add(this.mediaCollection[i]); //here addd the selected item to the lls
    i++;
}