Close, but hanging badly.

Source/FileManager/BackgroundFileSystem.cs

@@ -72,8 +72,8 @@ private void Init()
             fileSystemWatcher.Renamed += FileSystemWatcher_Changed;
             fileSystemWatcher.Error += FileSystemWatcher_Error;
 
-            backgroundScanner = new Task(BackgroundScanner);
-            backgroundScanner.Start();
+            backgroundScanner = Task.Factory.StartNew(BackgroundScanner, TaskCreationOptions.LongRunning);
+            //backgroundScanner.Start();
         }
         private void Stop()
         {

Source/LibationUiBase/ViewModels/Player/PlayerEvents.cs

@@ -8,7 +8,6 @@ public class BookAddedToPlaylist : PubSubEvent<ILibraryBookEntry>
         public ILibraryBookEntry Book { get; }
 
         public BookAddedToPlaylist() {}
-
         public BookAddedToPlaylist(ILibraryBookEntry book)
         {
             Book = book;
@@ -20,7 +19,6 @@ public class BookRemovedFromPlaylist : PubSubEvent<ILibraryBookEntry>
         public ILibraryBookEntry Book { get; }
 
         public BookRemovedFromPlaylist() {}
-
         public BookRemovedFromPlaylist(ILibraryBookEntry book)
         {
             Book = book;

Source/LibationUiBase/ViewModels/Player/PlayerViewModel.cs

@@ -8,8 +8,6 @@ namespace LibationUiBase.ViewModels.Player;
 
 public class PlayerViewModel : ViewModelBase
 {
-    const string CurrentIndicator = "▶";
-
     private readonly IEventAggregator eventAggregator;
     private BindingList<PlaylistEntryViewModel> playlistItems = new();
     /// <summary>
@@ -37,20 +35,28 @@ public PlayerViewModel(IEventAggregator eventAggregator)
         {
             playlistItems.MoveUp(SelectedBook);
             RenumberPlaylist();
-        }, _ => SelectedBook != null && playlistItems.IndexOf(SelectedBook) > 0);
+            var temp = SelectedBook;
+            SelectedBook = null;
+            SelectedBook = temp;
+        }, _ => SelectedBook != null && playlistItems.IndexOf(SelectedBook) > 0 &&
+                IsInPlaylist(SelectedBook));
 
         MoveDownCommand = new RelayCommand(_ =>
         {
             playlistItems.MoveDown(SelectedBook);
             RenumberPlaylist();
-        }, _ => SelectedBook != null && playlistItems.IndexOf(SelectedBook) < playlistItems.Count - 1);
+            var temp = SelectedBook;
+            SelectedBook = null;
+            SelectedBook = temp;
+        }, _ => SelectedBook != null && playlistItems.IndexOf(SelectedBook) < playlistItems.Count - 1 &&
+                IsInPlaylist(SelectedBook));
 
         this.eventAggregator = eventAggregator;
     }
 
     private void RenumberPlaylist()
     {
-        for (var i = 0; playlistItems.Count > 0; i++)
+        for (var i = 0; i < playlistItems.Count; i++)
             playlistItems[i].Sequence = i + 1;
     }
 
@@ -60,7 +66,7 @@ public async ValueTask AddToPlaylist(ILibraryBookEntry book)
         await plevm.Init(book);
         plevm.Sequence = playlistItems.Count + 1;
         playlistItems.Add(plevm);
-        eventAggregator.GetEvent<BookAddedToPlaylist>().Publish(book);
+        //eventAggregator.GetEvent<BookAddedToPlaylist>().Publish(book);
     }
 
     public ValueTask RemoveFromPlaylist(ILibraryBookEntry book)
@@ -69,27 +75,36 @@ public ValueTask RemoveFromPlaylist(ILibraryBookEntry book)
         if (plevm != null)
         {
             playlistItems.Remove(plevm);
-            eventAggregator.GetEvent<BookRemovedFromPlaylist>().Publish(book);
+            InvalidateCommands();
+            //eventAggregator.GetEvent<BookRemovedFromPlaylist>().Publish(book);
         }
 
         return ValueTask.CompletedTask;
     }
 
+    private void InvalidateCommands()
+    {
+        MoveDownCommand.RaiseCanExecuteChanged();
+        MoveUpCommand.RaiseCanExecuteChanged();
+    }
+
     public bool IsInPlaylist(ILibraryBookEntry book) =>
         PlaylistItems.Any(item => item.BookEntry.AudibleProductId == book.AudibleProductId);
 
-    public override string ToString() =>
-        string.Join(", ", playlistItems);
+    public bool IsInPlaylist(PlaylistEntryViewModel book) =>
+        PlaylistItems.Any(item => item.BookEntry.AudibleProductId == book.BookEntry.AudibleProductId);
+
+
+    public override string ToString() => $"{nameof(PlayerViewModel)}: {string.Join(", ", playlistItems)}";
 
     protected override void OnPropertyChanging(string propertyName)
     {
         switch (propertyName)
         {
             case nameof(SelectedBook):
-                //SelectedBook.IsCurrent = false;
-                //SelectedBook.IsCurrentStr = null;
-                MoveUpCommand.RaiseCanExecuteChanged();
-                MoveDownCommand.RaiseCanExecuteChanged();
+                if (SelectedBook != null)
+                    SelectedBook.IsCurrent = false;
+                InvalidateCommands();
                 break;
         }
     }
@@ -99,11 +114,10 @@ protected override void OnPropertyChanged(string propertyName)
         switch (propertyName)
         {
             case nameof(SelectedBook):
-                MoveDownCommand.RaiseCanExecuteChanged();
-                MoveUpCommand.RaiseCanExecuteChanged();
-                //SelectedBook.IsCurrent = true;
-                //SelectedBook.IsCurrentStr = CurrentIndicator;
+                if (SelectedBook != null)
+                    SelectedBook.IsCurrent = true;
+                InvalidateCommands();
                 break;
         }
     }
-}
+}

Source/LibationUiBase/ViewModels/Player/PlaylistEntryViewModel.cs

@@ -5,6 +5,8 @@ namespace LibationUiBase.ViewModels.Player;
 
 public class PlaylistEntryViewModel : ViewModelBase
 {
+    const string CurrentIndicator = "▶";
+
     private int sequence;
     public int Sequence
     {
@@ -50,4 +52,21 @@ public async ValueTask Init(ILibraryBookEntry bookEntry)
     }
 
     public override string ToString() => Title;
+
+    protected override void OnPropertyChanged(string propertyName)
+    {
+        switch (propertyName)
+        {
+            case nameof(IsCurrent):
+                IsCurrentStr = IsCurrent ? CurrentIndicator : null;
+                break;
+        }
+    }
+
+    public override bool Equals(object obj)
+    {
+        if (obj is PlaylistEntryViewModel plevm && bookEntry != null)
+            return bookEntry?.AudibleProductId == plevm?.bookEntry.AudibleProductId;
+        return false;
+    }
 }

Source/LibationUiBase/ViewModels/ViewModelBase.cs

@@ -8,16 +8,16 @@ public abstract class ViewModelBase : INotifyPropertyChanged, INotifyPropertyCha
 {
     public ViewModelBase()
     {
-        this.PropertyChanged += (s, e) => OnPropertyChanged(e.PropertyName);
-        this.PropertyChanging += (s, e) => OnPropertyChanging(e.PropertyName);
+        this.PropertyChanged += (_, e) => OnPropertyChanged(e.PropertyName);
+        this.PropertyChanging += (_, e) => OnPropertyChanging(e.PropertyName);
     }
 
     protected virtual void OnPropertyChanging(string propertyName) { }
     protected virtual void OnPropertyChanged(string propertyName) { }
 
     public TRet RaiseAndSetIfChanged<TRet>(ref TRet backingField, TRet newValue, [CallerMemberName] string propertyName = null)
     {
-        //if (EqualityComparer<TRet>.Default.Equals(backingField, newValue)) return newValue;
+        if (EqualityComparer<TRet>.Default.Equals(backingField, newValue)) return newValue;
 
         RaisePropertyChanging(propertyName);
         backingField = newValue;