Merge branch 'master' into authenticationdb-efcore

# Conflicts:
#	Emby.Server.Implementations/Devices/DeviceManager.cs
#	Emby.Server.Implementations/HttpServer/Security/SessionContext.cs
#	Emby.Server.Implementations/Security/AuthenticationRepository.cs
#	Emby.Server.Implementations/Session/SessionManager.cs
#	Jellyfin.Server.Implementations/Security/AuthorizationContext.cs
#	MediaBrowser.Controller/Library/IUserManager.cs
#	MediaBrowser.Controller/Net/ISessionContext.cs

17 files changed, 126 insertions, 81 deletions

diff --git a/MediaBrowser.Controller/Entities/AggregateFolder.cs b/MediaBrowser.Controller/Entities/AggregateFolder.cs
index 533130fc8..fe1bc62ab 100644
--- a/MediaBrowser.Controller/Entities/AggregateFolder.cs
+++ b/MediaBrowser.Controller/Entities/AggregateFolder.cs
@@ -155,11 +155,11 @@ namespace MediaBrowser.Controller.Entities
             return base.GetNonCachedChildren(directoryService).Concat(_virtualChildren);
         }
 
-        protected override async Task ValidateChildrenInternal(IProgress<double> progress, CancellationToken cancellationToken, bool recursive, bool refreshChildMetadata, MetadataRefreshOptions refreshOptions, IDirectoryService directoryService)
+        protected override async Task ValidateChildrenInternal(IProgress<double> progress, bool recursive, bool refreshChildMetadata, MetadataRefreshOptions refreshOptions, IDirectoryService directoryService, CancellationToken cancellationToken)
         {
             ClearCache();
 
-            await base.ValidateChildrenInternal(progress, cancellationToken, recursive, refreshChildMetadata, refreshOptions, directoryService)
+            await base.ValidateChildrenInternal(progress, recursive, refreshChildMetadata, refreshOptions, directoryService, cancellationToken)
                 .ConfigureAwait(false);
 
             ClearCache();
@@ -185,7 +185,7 @@ namespace MediaBrowser.Controller.Entities
         /// </summary>
         /// <param name="id">The id.</param>
         /// <returns>BaseItem.</returns>
-        /// <exception cref="ArgumentNullException">id</exception>
+        /// <exception cref="ArgumentNullException">The id is empty.</exception>
         public BaseItem FindVirtualChild(Guid id)
         {
             if (id.Equals(Guid.Empty))
diff --git a/MediaBrowser.Controller/Entities/Audio/Audio.cs b/MediaBrowser.Controller/Entities/Audio/Audio.cs
index 4c2b7cb7c..576ab67a2 100644
--- a/MediaBrowser.Controller/Entities/Audio/Audio.cs
+++ b/MediaBrowser.Controller/Entities/Audio/Audio.cs
@@ -4,6 +4,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Globalization;
 using System.Linq;
 using System.Text.Json.Serialization;
 using Jellyfin.Data.Enums;
@@ -82,19 +83,19 @@ namespace MediaBrowser.Controller.Entities.Audio
         /// <returns>System.String.</returns>
         protected override string CreateSortName()
         {
-            return (ParentIndexNumber != null ? ParentIndexNumber.Value.ToString("0000 - ") : "")
-                    + (IndexNumber != null ? IndexNumber.Value.ToString("0000 - ") : "") + Name;
+            return (ParentIndexNumber != null ? ParentIndexNumber.Value.ToString("0000 - ", CultureInfo.InvariantCulture) : string.Empty)
+                    + (IndexNumber != null ? IndexNumber.Value.ToString("0000 - ", CultureInfo.InvariantCulture) : string.Empty) + Name;
         }
 
         public override List<string> GetUserDataKeys()
         {
             var list = base.GetUserDataKeys();
 
-            var songKey = IndexNumber.HasValue ? IndexNumber.Value.ToString("0000") : string.Empty;
+            var songKey = IndexNumber.HasValue ? IndexNumber.Value.ToString("0000", CultureInfo.InvariantCulture) : string.Empty;
 
             if (ParentIndexNumber.HasValue)
             {
-                songKey = ParentIndexNumber.Value.ToString("0000") + "-" + songKey;
+                songKey = ParentIndexNumber.Value.ToString("0000", CultureInfo.InvariantCulture) + "-" + songKey;
             }
 
             songKey += Name;
diff --git a/MediaBrowser.Controller/Entities/Audio/MusicArtist.cs b/MediaBrowser.Controller/Entities/Audio/MusicArtist.cs
index 0928a8073..c0cd81110 100644
--- a/MediaBrowser.Controller/Entities/Audio/MusicArtist.cs
+++ b/MediaBrowser.Controller/Entities/Audio/MusicArtist.cs
@@ -94,7 +94,7 @@ namespace MediaBrowser.Controller.Entities.Audio
             return base.IsSaveLocalMetadataEnabled();
         }
 
-        protected override Task ValidateChildrenInternal(IProgress<double> progress, CancellationToken cancellationToken, bool recursive, bool refreshChildMetadata, MetadataRefreshOptions refreshOptions, IDirectoryService directoryService)
+        protected override Task ValidateChildrenInternal(IProgress<double> progress, bool recursive, bool refreshChildMetadata, MetadataRefreshOptions refreshOptions, IDirectoryService directoryService, CancellationToken cancellationToken)
         {
             if (IsAccessedByName)
             {
@@ -102,7 +102,7 @@ namespace MediaBrowser.Controller.Entities.Audio
                 return Task.CompletedTask;
             }
 
-            return base.ValidateChildrenInternal(progress, cancellationToken, recursive, refreshChildMetadata, refreshOptions, directoryService);
+            return base.ValidateChildrenInternal(progress, recursive, refreshChildMetadata, refreshOptions, directoryService, cancellationToken);
         }
 
         public override List<string> GetUserDataKeys()
diff --git a/MediaBrowser.Controller/Entities/BaseItem.cs b/MediaBrowser.Controller/Entities/BaseItem.cs
index 6e46b4cec..6137ddbf7 100644
--- a/MediaBrowser.Controller/Entities/BaseItem.cs
+++ b/MediaBrowser.Controller/Entities/BaseItem.cs
@@ -620,7 +620,11 @@ namespace MediaBrowser.Controller.Entities
         public string ForcedSortName
         {
             get => _forcedSortName;
-            set { _forcedSortName = value; _sortName = null; }
+            set
+            {
+                _forcedSortName = value;
+                _sortName = null;
+            }
         }
 
         private string _sortName;
@@ -666,14 +670,12 @@ namespace MediaBrowser.Controller.Entities
         {
             if (SourceType == SourceType.Channel)
             {
-                return System.IO.Path.Combine(basePath, "channels", ChannelId.ToString("N", CultureInfo.InvariantCulture), Id.ToString("N", CultureInfo.InvariantCulture));
+                return System.IO.Path.Join(basePath, "channels", ChannelId.ToString("N", CultureInfo.InvariantCulture), Id.ToString("N", CultureInfo.InvariantCulture));
             }
 
             ReadOnlySpan<char> idString = Id.ToString("N", CultureInfo.InvariantCulture);
 
-            basePath = System.IO.Path.Combine(basePath, "library");
-
-            return System.IO.Path.Join(basePath, idString.Slice(0, 2), idString);
+            return System.IO.Path.Join(basePath, "library", idString.Slice(0, 2), idString);
         }
 
         /// <summary>
@@ -1258,7 +1260,7 @@ namespace MediaBrowser.Controller.Entities
 
             // Support plex/xbmc convention
             files.AddRange(fileSystemChildren
-                .Where(i => !i.IsDirectory && string.Equals(FileSystem.GetFileNameWithoutExtension(i), ThemeSongFilename, StringComparison.OrdinalIgnoreCase)));
+                .Where(i => !i.IsDirectory && System.IO.Path.GetFileNameWithoutExtension(i.FullName.AsSpan()).Equals(ThemeSongFilename, StringComparison.OrdinalIgnoreCase)));
 
             return LibraryManager.ResolvePaths(files, directoryService, null, new LibraryOptions())
                 .OfType<Audio.Audio>()
@@ -1319,14 +1321,16 @@ namespace MediaBrowser.Controller.Entities
         {
             var extras = new List<Video>();
 
-            var folders = fileSystemChildren.Where(i => i.IsDirectory).ToArray();
+            var libraryOptions = new LibraryOptions();
+            var folders = fileSystemChildren.Where(i => i.IsDirectory).ToList();
             foreach (var extraFolderName in AllExtrasTypesFolderNames)
             {
                 var files = folders
                     .Where(i => string.Equals(i.Name, extraFolderName, StringComparison.OrdinalIgnoreCase))
                     .SelectMany(i => FileSystem.GetFiles(i.FullName));
 
-                extras.AddRange(LibraryManager.ResolvePaths(files, directoryService, null, new LibraryOptions())
+                // Re-using the same instance of LibraryOptions since it looks like it's never being altered.
+                extras.AddRange(LibraryManager.ResolvePaths(files, directoryService, null, libraryOptions)
                     .OfType<Video>()
                     .Select(item =>
                     {
@@ -1337,7 +1341,7 @@ namespace MediaBrowser.Controller.Entities
                         }
 
                         // Use some hackery to get the extra type based on foldername
-                        item.ExtraType = Enum.TryParse(extraFolderName.Replace(" ", string.Empty), true, out ExtraType extraType)
+                        item.ExtraType = Enum.TryParse(extraFolderName.Replace(" ", string.Empty, StringComparison.Ordinal), true, out ExtraType extraType)
                             ? extraType
                             : Model.Entities.ExtraType.Unknown;
 
@@ -1427,10 +1431,10 @@ namespace MediaBrowser.Controller.Entities
         /// Refreshes owned items such as trailers, theme videos, special features, etc.
         /// Returns true or false indicating if changes were found.
         /// </summary>
-        /// <param name="options"></param>
-        /// <param name="fileSystemChildren"></param>
-        /// <param name="cancellationToken"></param>
-        /// <returns></returns>
+        /// <param name="options">The metadata refresh options.</param>
+        /// <param name="fileSystemChildren">The list of filesystem children.</param>
+        /// <param name="cancellationToken">The cancellation token.</param>
+        /// <returns><c>true</c> if any items have changed, else <c>false</c>.</returns>
         protected virtual async Task<bool> RefreshedOwnedItems(MetadataRefreshOptions options, List<FileSystemMetadata> fileSystemChildren, CancellationToken cancellationToken)
         {
             var themeSongsChanged = false;
@@ -1772,7 +1776,7 @@ namespace MediaBrowser.Controller.Entities
         /// </summary>
         /// <param name="user">The user.</param>
         /// <returns><c>true</c> if [is parental allowed] [the specified user]; otherwise, <c>false</c>.</returns>
-        /// <exception cref="ArgumentNullException">user</exception>
+        /// <exception cref="ArgumentNullException">If user is null.</exception>
         public bool IsParentalAllowed(User user)
         {
             if (user == null)
@@ -1917,7 +1921,7 @@ namespace MediaBrowser.Controller.Entities
         /// </summary>
         /// <param name="user">The user.</param>
         /// <returns><c>true</c> if the specified user is visible; otherwise, <c>false</c>.</returns>
-        /// <exception cref="ArgumentNullException">user</exception>
+        /// <exception cref="ArgumentNullException"><paramref name="user" /> is <c>null</c>.</exception>
         public virtual bool IsVisible(User user)
         {
             if (user == null)
@@ -2215,7 +2219,7 @@ namespace MediaBrowser.Controller.Entities
         /// <param name="type">The type.</param>
         /// <param name="imageIndex">Index of the image.</param>
         /// <returns><c>true</c> if the specified type has image; otherwise, <c>false</c>.</returns>
-        /// <exception cref="ArgumentException">Backdrops should be accessed using Item.Backdrops</exception>
+        /// <exception cref="ArgumentException">Backdrops should be accessed using Item.Backdrops.</exception>
         public bool HasImage(ImageType type, int imageIndex)
         {
             return GetImageInfo(type, imageIndex) != null;
@@ -2323,7 +2327,7 @@ namespace MediaBrowser.Controller.Entities
                 .Where(i => i.IsLocalFile)
                 .Select(i => System.IO.Path.GetDirectoryName(i.Path))
                 .Distinct(StringComparer.OrdinalIgnoreCase)
-                .SelectMany(directoryService.GetFilePaths)
+                .SelectMany(path => directoryService.GetFilePaths(path))
                 .ToList();
 
             var deletedImages = ImageInfos
@@ -2344,9 +2348,8 @@ namespace MediaBrowser.Controller.Entities
         /// <param name="imageType">Type of the image.</param>
         /// <param name="imageIndex">Index of the image.</param>
         /// <returns>System.String.</returns>
-        /// <exception cref="InvalidOperationException">
-        /// </exception>
-        /// <exception cref="ArgumentNullException">item</exception>
+        /// <exception cref="InvalidOperationException"> </exception>
+        /// <exception cref="ArgumentNullException">Item is null.</exception>
         public string GetImagePath(ImageType imageType, int imageIndex)
             => GetImageInfo(imageType, imageIndex)?.Path;
 
@@ -2433,7 +2436,15 @@ namespace MediaBrowser.Controller.Entities
                 throw new ArgumentException("No image info for chapter images");
             }
 
-            return ImageInfos.Where(i => i.Type == imageType);
+            // Yield return is more performant than LINQ Where on an Array
+            for (var i = 0; i < ImageInfos.Length; i++)
+            {
+                var imageInfo = ImageInfos[i];
+                if (imageInfo.Type == imageType)
+                {
+                    yield return imageInfo;
+                }
+            }
         }
 
         /// <summary>
@@ -2442,7 +2453,7 @@ namespace MediaBrowser.Controller.Entities
         /// <param name="imageType">Type of the image.</param>
         /// <param name="images">The images.</param>
         /// <returns><c>true</c> if XXXX, <c>false</c> otherwise.</returns>
-        /// <exception cref="ArgumentException">Cannot call AddImages with chapter images</exception>
+        /// <exception cref="ArgumentException">Cannot call AddImages with chapter images.</exception>
         public bool AddImages(ImageType imageType, List<FileSystemMetadata> images)
         {
             if (imageType == ImageType.Chapter)
@@ -2465,7 +2476,7 @@ namespace MediaBrowser.Controller.Entities
                 }
 
                 var existing = existingImages
-                    .FirstOrDefault(i => string.Equals(i.Path, newImage.FullName, StringComparison.OrdinalIgnoreCase));
+                    .Find(i => string.Equals(i.Path, newImage.FullName, StringComparison.OrdinalIgnoreCase));
 
                 if (existing == null)
                 {
@@ -2496,8 +2507,7 @@ namespace MediaBrowser.Controller.Entities
                 var newImagePaths = images.Select(i => i.FullName).ToList();
 
                 var deleted = existingImages
-                    .Where(i => i.IsLocalFile && !newImagePaths.Contains(i.Path, StringComparer.OrdinalIgnoreCase) && !File.Exists(i.Path))
-                    .ToList();
+                    .FindAll(i => i.IsLocalFile && !newImagePaths.Contains(i.Path.AsSpan(), StringComparison.OrdinalIgnoreCase) && !File.Exists(i.Path));
 
                 if (deleted.Count > 0)
                 {
@@ -2526,10 +2536,11 @@ namespace MediaBrowser.Controller.Entities
         /// <summary>
         /// Gets the file system path to delete when the item is to be deleted.
         /// </summary>
-        /// <returns></returns>
+        /// <returns>The metadata for the deleted paths.</returns>
         public virtual IEnumerable<FileSystemMetadata> GetDeletePaths()
         {
-            return new[] {
+            return new[]
+            {
                 new FileSystemMetadata
                 {
                     FullName = Path,
@@ -2636,6 +2647,7 @@ namespace MediaBrowser.Controller.Entities
                 MetadataCountryCode = GetPreferredMetadataCountryCode(),
                 MetadataLanguage = GetPreferredMetadataLanguage(),
                 Name = GetNameForMetadataLookup(),
+                OriginalTitle = OriginalTitle,
                 ProviderIds = ProviderIds,
                 IndexNumber = IndexNumber,
                 ParentIndexNumber = ParentIndexNumber,
@@ -2889,7 +2901,7 @@ namespace MediaBrowser.Controller.Entities
         /// <summary>
         /// Updates the official rating based on content and returns true or false indicating if it changed.
         /// </summary>
-        /// <returns></returns>
+        /// <returns><c>true</c> if the rating was updated; otherwise <c>false</c>.</returns>
         public bool UpdateRatingToItems(IList<BaseItem> children)
         {
             var currentOfficialRating = OfficialRating;
@@ -2905,7 +2917,9 @@ namespace MediaBrowser.Controller.Entities
 
             OfficialRating = ratings.FirstOrDefault() ?? currentOfficialRating;
 
-            return !string.Equals(currentOfficialRating ?? string.Empty, OfficialRating ?? string.Empty,
+            return !string.Equals(
+                currentOfficialRating ?? string.Empty,
+                OfficialRating ?? string.Empty,
                 StringComparison.OrdinalIgnoreCase);
         }
 
@@ -3002,7 +3016,7 @@ namespace MediaBrowser.Controller.Entities
         }
 
         /// <inheritdoc />
-        public bool Equals(BaseItem item) => Object.Equals(Id, item?.Id);
+        public bool Equals(BaseItem other) => object.Equals(Id, other?.Id);
 
         /// <inheritdoc />
         public override int GetHashCode() => HashCode.Combine(Id);
diff --git a/MediaBrowser.Controller/Entities/BaseItemExtensions.cs b/MediaBrowser.Controller/Entities/BaseItemExtensions.cs
index c39b18891..89ad392a4 100644
--- a/MediaBrowser.Controller/Entities/BaseItemExtensions.cs
+++ b/MediaBrowser.Controller/Entities/BaseItemExtensions.cs
@@ -1,6 +1,3 @@
-#nullable disable
-
-#nullable enable
 #pragma warning disable CS1591
 
 using System;
diff --git a/MediaBrowser.Controller/Entities/CollectionFolder.cs b/MediaBrowser.Controller/Entities/CollectionFolder.cs
index d0fb3997d..4a721ca44 100644
--- a/MediaBrowser.Controller/Entities/CollectionFolder.cs
+++ b/MediaBrowser.Controller/Entities/CollectionFolder.cs
@@ -315,16 +315,16 @@ namespace MediaBrowser.Controller.Entities
 
         /// <summary>
         /// Compare our current children (presumably just read from the repo) with the current state of the file system and adjust for any changes
-        /// ***Currently does not contain logic to maintain items that are unavailable in the file system***
+        /// ***Currently does not contain logic to maintain items that are unavailable in the file system***.
         /// </summary>
         /// <param name="progress">The progress.</param>
-        /// <param name="cancellationToken">The cancellation token.</param>
         /// <param name="recursive">if set to <c>true</c> [recursive].</param>
         /// <param name="refreshChildMetadata">if set to <c>true</c> [refresh child metadata].</param>
         /// <param name="refreshOptions">The refresh options.</param>
         /// <param name="directoryService">The directory service.</param>
+        /// <param name="cancellationToken">The cancellation token.</param>
         /// <returns>Task.</returns>
-        protected override Task ValidateChildrenInternal(IProgress<double> progress, CancellationToken cancellationToken, bool recursive, bool refreshChildMetadata, MetadataRefreshOptions refreshOptions, IDirectoryService directoryService)
+        protected override Task ValidateChildrenInternal(IProgress<double> progress, bool recursive, bool refreshChildMetadata, MetadataRefreshOptions refreshOptions, IDirectoryService directoryService, CancellationToken cancellationToken)
         {
             return Task.CompletedTask;
         }
diff --git a/MediaBrowser.Controller/Entities/Folder.cs b/MediaBrowser.Controller/Entities/Folder.cs
index 29d837c14..541747422 100644
--- a/MediaBrowser.Controller/Entities/Folder.cs
+++ b/MediaBrowser.Controller/Entities/Folder.cs
@@ -207,8 +207,7 @@ namespace MediaBrowser.Controller.Entities
         /// </summary>
         /// <param name="item">The item.</param>
         /// <param name="cancellationToken">The cancellation token.</param>
-        /// <returns>Task.</returns>
-        /// <exception cref="InvalidOperationException">Unable to add  + item.Name</exception>
+        /// <exception cref="InvalidOperationException">Unable to add  + item.Name.</exception>
         public void AddChild(BaseItem item, CancellationToken cancellationToken)
         {
             item.SetParent(this);
@@ -274,20 +273,20 @@ namespace MediaBrowser.Controller.Entities
 
         public Task ValidateChildren(IProgress<double> progress, CancellationToken cancellationToken)
         {
-            return ValidateChildren(progress, cancellationToken, new MetadataRefreshOptions(new DirectoryService(FileSystem)));
+            return ValidateChildren(progress, new MetadataRefreshOptions(new DirectoryService(FileSystem)), cancellationToken: cancellationToken);
         }
 
         /// <summary>
         /// Validates that the children of the folder still exist.
         /// </summary>
         /// <param name="progress">The progress.</param>
-        /// <param name="cancellationToken">The cancellation token.</param>
         /// <param name="metadataRefreshOptions">The metadata refresh options.</param>
         /// <param name="recursive">if set to <c>true</c> [recursive].</param>
+        /// <param name="cancellationToken">The cancellation token.</param>
         /// <returns>Task.</returns>
-        public Task ValidateChildren(IProgress<double> progress, CancellationToken cancellationToken, MetadataRefreshOptions metadataRefreshOptions, bool recursive = true)
+        public Task ValidateChildren(IProgress<double> progress, MetadataRefreshOptions metadataRefreshOptions, bool recursive = true,  CancellationToken cancellationToken = default)
         {
-            return ValidateChildrenInternal(progress, cancellationToken, recursive, true, metadataRefreshOptions, metadataRefreshOptions.DirectoryService);
+            return ValidateChildrenInternal(progress, recursive, true, metadataRefreshOptions, metadataRefreshOptions.DirectoryService, cancellationToken);
         }
 
         private Dictionary<Guid, BaseItem> GetActualChildrenDictionary()
@@ -327,13 +326,13 @@ namespace MediaBrowser.Controller.Entities
         /// Validates the children internal.
         /// </summary>
         /// <param name="progress">The progress.</param>
-        /// <param name="cancellationToken">The cancellation token.</param>
         /// <param name="recursive">if set to <c>true</c> [recursive].</param>
         /// <param name="refreshChildMetadata">if set to <c>true</c> [refresh child metadata].</param>
         /// <param name="refreshOptions">The refresh options.</param>
         /// <param name="directoryService">The directory service.</param>
+        /// <param name="cancellationToken">The cancellation token.</param>
         /// <returns>Task.</returns>
-        protected virtual async Task ValidateChildrenInternal(IProgress<double> progress, CancellationToken cancellationToken, bool recursive, bool refreshChildMetadata, MetadataRefreshOptions refreshOptions, IDirectoryService directoryService)
+        protected virtual async Task ValidateChildrenInternal(IProgress<double> progress, bool recursive, bool refreshChildMetadata, MetadataRefreshOptions refreshOptions, IDirectoryService directoryService, CancellationToken cancellationToken)
         {
             if (recursive)
             {
@@ -342,7 +341,7 @@ namespace MediaBrowser.Controller.Entities
 
             try
             {
-                await ValidateChildrenInternal2(progress, cancellationToken, recursive, refreshChildMetadata, refreshOptions, directoryService).ConfigureAwait(false);
+                await ValidateChildrenInternal2(progress, recursive, refreshChildMetadata, refreshOptions, directoryService, cancellationToken).ConfigureAwait(false);
             }
             finally
             {
@@ -353,7 +352,7 @@ namespace MediaBrowser.Controller.Entities
             }
         }
 
-        private async Task ValidateChildrenInternal2(IProgress<double> progress, CancellationToken cancellationToken, bool recursive, bool refreshChildMetadata, MetadataRefreshOptions refreshOptions, IDirectoryService directoryService)
+        private async Task ValidateChildrenInternal2(IProgress<double> progress, bool recursive, bool refreshChildMetadata, MetadataRefreshOptions refreshOptions, IDirectoryService directoryService, CancellationToken cancellationToken)
         {
             cancellationToken.ThrowIfCancellationRequested();
 
@@ -575,7 +574,7 @@ namespace MediaBrowser.Controller.Entities
         private Task ValidateSubFolders(IList<Folder> children, IDirectoryService directoryService, IProgress<double> progress, CancellationToken cancellationToken)
         {
             return RunTasks(
-                (folder, innerProgress) => folder.ValidateChildrenInternal(innerProgress, cancellationToken, true, false, null, directoryService),
+                (folder, innerProgress) => folder.ValidateChildrenInternal(innerProgress, true, false, null, directoryService, cancellationToken),
                 children,
                 progress,
                 cancellationToken);
@@ -988,7 +987,13 @@ namespace MediaBrowser.Controller.Entities
             }
             else
             {
-                items = GetChildren(user, true).Where(filter);
+                // need to pass this param to the children.
+                var childQuery = new InternalItemsQuery
+                {
+                    DisplayAlbumFolders = query.DisplayAlbumFolders
+                };
+
+                items = GetChildren(user, true, childQuery).Where(filter);
             }
 
             return PostFilterAndSort(items, query, true);
@@ -1013,7 +1018,7 @@ namespace MediaBrowser.Controller.Entities
 
             if (!string.IsNullOrEmpty(query.NameStartsWith))
             {
-                items = items.Where(i => i.SortName.StartsWith(query.NameStartsWith, StringComparison.OrdinalIgnoreCase));
+                items = items.Where(i => i.SortName.StartsWith(query.NameStartsWith, StringComparison.CurrentCultureIgnoreCase));
             }
 
             if (!string.IsNullOrEmpty(query.NameLessThan))
@@ -1324,10 +1329,23 @@ namespace MediaBrowser.Controller.Entities
         /// <summary>
         /// Adds the children to list.
         /// </summary>
-        /// <returns><c>true</c> if XXXX, <c>false</c> otherwise</returns>
         private void AddChildren(User user, bool includeLinkedChildren, Dictionary<Guid, BaseItem> result, bool recursive, InternalItemsQuery query)
         {
-            foreach (var child in GetEligibleChildrenForRecursiveChildren(user))
+            // If Query.AlbumFolders is set, then enforce the format as per the db in that it permits sub-folders in music albums.
+            IEnumerable<BaseItem> children = null;
+            if ((query?.DisplayAlbumFolders ?? false) && (this is MusicAlbum))
+            {
+                children = Children;
+                query = null;
+            }
+
+            // If there are not sub-folders, proceed as normal.
+            if (children == null)
+            {
+                children = GetEligibleChildrenForRecursiveChildren(user);
+            }
+
+            foreach (var child in children)
             {
                 bool? isVisibleToUser = null;
 
@@ -1596,7 +1614,8 @@ namespace MediaBrowser.Controller.Entities
         /// <summary>
         /// Refreshes the linked children.
         /// </summary>
-        /// <returns><c>true</c> if XXXX, <c>false</c> otherwise</returns>
+        /// <param name="fileSystemChildren">The enumerable of file system metadata.</param>
+        /// <returns><c>true</c> if the linked children were updated, <c>false</c> otherwise.</returns>
         protected virtual bool RefreshLinkedChildren(IEnumerable<FileSystemMetadata> fileSystemChildren)
         {
             if (SupportsShortcutChildren)
diff --git a/MediaBrowser.Controller/Entities/Genre.cs b/MediaBrowser.Controller/Entities/Genre.cs
index 698643b44..b80a5be3b 100644
--- a/MediaBrowser.Controller/Entities/Genre.cs
+++ b/MediaBrowser.Controller/Entities/Genre.cs
@@ -107,7 +107,11 @@ namespace MediaBrowser.Controller.Entities
             return base.RequiresRefresh();
         }
 
-        /// <inheridoc />
+        /// <summary>
+        /// This is called before any metadata refresh and returns true if changes were made.
+        /// </summary>
+        /// <param name="replaceAllMetadata">Whether to replace all metadata.</param>
+        /// <returns>true if the item has change, else false.</returns>
         public override bool BeforeMetadataRefresh(bool replaceAllMetadata)
         {
             var hasChanges = base.BeforeMetadataRefresh(replaceAllMetadata);
diff --git a/MediaBrowser.Controller/Entities/IHasScreenshots.cs b/MediaBrowser.Controller/Entities/IHasScreenshots.cs
index b027a0cb1..ae01c223e 100644
--- a/MediaBrowser.Controller/Entities/IHasScreenshots.cs
+++ b/MediaBrowser.Controller/Entities/IHasScreenshots.cs
@@ -1,7 +1,7 @@
 namespace MediaBrowser.Controller.Entities
 {
     /// <summary>
-    /// Interface IHasScreenshots.
+    /// The item has screenshots.
     /// </summary>
     public interface IHasScreenshots
     {
diff --git a/MediaBrowser.Controller/Entities/InternalItemsQuery.cs b/MediaBrowser.Controller/Entities/InternalItemsQuery.cs
index 75fea365b..ebaf5506d 100644
--- a/MediaBrowser.Controller/Entities/InternalItemsQuery.cs
+++ b/MediaBrowser.Controller/Entities/InternalItemsQuery.cs
@@ -265,6 +265,11 @@ namespace MediaBrowser.Controller.Entities
 
         public bool? IsDeadPerson { get; set; }
 
+        /// <summary>
+        /// Gets or sets a value indicating whether album sub-folders should be returned if they exist.
+        /// </summary>
+        public bool? DisplayAlbumFolders { get; set; }
+
         public InternalItemsQuery()
         {
             AlbumArtistIds = Array.Empty<Guid>();
diff --git a/MediaBrowser.Controller/Entities/LinkedChildComparer.cs b/MediaBrowser.Controller/Entities/LinkedChildComparer.cs
index 66fc44b8a..4e58e2942 100644
--- a/MediaBrowser.Controller/Entities/LinkedChildComparer.cs
+++ b/MediaBrowser.Controller/Entities/LinkedChildComparer.cs
@@ -2,6 +2,7 @@
 
 #pragma warning disable CS1591
 
+using System;
 using System.Collections.Generic;
 using MediaBrowser.Model.IO;
 
@@ -28,7 +29,7 @@ namespace MediaBrowser.Controller.Entities
 
         public int GetHashCode(LinkedChild obj)
         {
-            return ((obj.Path ?? string.Empty) + (obj.LibraryItemId ?? string.Empty) + obj.Type).GetHashCode();
+            return ((obj.Path ?? string.Empty) + (obj.LibraryItemId ?? string.Empty) + obj.Type).GetHashCode(StringComparison.Ordinal);
         }
     }
 }
\ No newline at end of file
diff --git a/MediaBrowser.Controller/Entities/TV/Episode.cs b/MediaBrowser.Controller/Entities/TV/Episode.cs
index 1b4cc7a78..31c179bca 100644
--- a/MediaBrowser.Controller/Entities/TV/Episode.cs
+++ b/MediaBrowser.Controller/Entities/TV/Episode.cs
@@ -218,8 +218,8 @@ namespace MediaBrowser.Controller.Entities.TV
         /// <returns>System.String.</returns>
         protected override string CreateSortName()
         {
-            return (ParentIndexNumber != null ? ParentIndexNumber.Value.ToString("000 - ") : "")
-                    + (IndexNumber != null ? IndexNumber.Value.ToString("0000 - ") : "") + Name;
+            return (ParentIndexNumber != null ? ParentIndexNumber.Value.ToString("000 - ", CultureInfo.InvariantCulture) : string.Empty)
+                    + (IndexNumber != null ? IndexNumber.Value.ToString("0000 - ", CultureInfo.InvariantCulture) : string.Empty) + Name;
         }
 
         /// <summary>
@@ -287,7 +287,8 @@ namespace MediaBrowser.Controller.Entities.TV
 
         public override IEnumerable<FileSystemMetadata> GetDeletePaths()
         {
-            return new[] {
+            return new[]
+            {
                 new FileSystemMetadata
                 {
                     FullName = Path,
diff --git a/MediaBrowser.Controller/Entities/TV/Season.cs b/MediaBrowser.Controller/Entities/TV/Season.cs
index 5e2053dcc..aa62bb35b 100644
--- a/MediaBrowser.Controller/Entities/TV/Season.cs
+++ b/MediaBrowser.Controller/Entities/TV/Season.cs
@@ -122,7 +122,7 @@ namespace MediaBrowser.Controller.Entities.TV
                 var series = Series;
                 if (series != null)
                 {
-                    return series.PresentationUniqueKey + "-" + (IndexNumber ?? 0).ToString("000");
+                    return series.PresentationUniqueKey + "-" + (IndexNumber ?? 0).ToString("000", CultureInfo.InvariantCulture);
                 }
             }
 
@@ -135,7 +135,7 @@ namespace MediaBrowser.Controller.Entities.TV
         /// <returns>System.String.</returns>
         protected override string CreateSortName()
         {
-            return IndexNumber != null ? IndexNumber.Value.ToString("0000") : Name;
+            return IndexNumber != null ? IndexNumber.Value.ToString("0000", CultureInfo.InvariantCulture) : Name;
         }
 
         protected override QueryResult<BaseItem> GetItemsInternal(InternalItemsQuery query)
diff --git a/MediaBrowser.Controller/Entities/UserRootFolder.cs b/MediaBrowser.Controller/Entities/UserRootFolder.cs
index 2dea2e50b..2b15a52f0 100644
--- a/MediaBrowser.Controller/Entities/UserRootFolder.cs
+++ b/MediaBrowser.Controller/Entities/UserRootFolder.cs
@@ -109,11 +109,11 @@ namespace MediaBrowser.Controller.Entities
             return base.GetNonCachedChildren(directoryService);
         }
 
-        protected override async Task ValidateChildrenInternal(IProgress<double> progress, CancellationToken cancellationToken, bool recursive, bool refreshChildMetadata, MetadataRefreshOptions refreshOptions, IDirectoryService directoryService)
+        protected override async Task ValidateChildrenInternal(IProgress<double> progress, bool recursive, bool refreshChildMetadata, MetadataRefreshOptions refreshOptions, IDirectoryService directoryService, CancellationToken cancellationToken)
         {
             ClearCache();
 
-            await base.ValidateChildrenInternal(progress, cancellationToken, recursive, refreshChildMetadata, refreshOptions, directoryService)
+            await base.ValidateChildrenInternal(progress, recursive, refreshChildMetadata, refreshOptions, directoryService, cancellationToken)
                 .ConfigureAwait(false);
 
             ClearCache();
diff --git a/MediaBrowser.Controller/Entities/UserView.cs b/MediaBrowser.Controller/Entities/UserView.cs
index 1e6c01bf8..57dc9b59b 100644
--- a/MediaBrowser.Controller/Entities/UserView.cs
+++ b/MediaBrowser.Controller/Entities/UserView.cs
@@ -172,7 +172,7 @@ namespace MediaBrowser.Controller.Entities
             return OriginalFolderViewTypes.Contains(viewType ?? string.Empty, StringComparer.OrdinalIgnoreCase);
         }
 
-        protected override Task ValidateChildrenInternal(IProgress<double> progress, System.Threading.CancellationToken cancellationToken, bool recursive, bool refreshChildMetadata, Providers.MetadataRefreshOptions refreshOptions, Providers.IDirectoryService directoryService)
+        protected override Task ValidateChildrenInternal(IProgress<double> progress, bool recursive, bool refreshChildMetadata, Providers.MetadataRefreshOptions refreshOptions, Providers.IDirectoryService directoryService, System.Threading.CancellationToken cancellationToken)
         {
             return Task.CompletedTask;
         }
diff --git a/MediaBrowser.Controller/Entities/UserViewBuilder.cs b/MediaBrowser.Controller/Entities/UserViewBuilder.cs
index 15a4573c2..add734f62 100644
--- a/MediaBrowser.Controller/Entities/UserViewBuilder.cs
+++ b/MediaBrowser.Controller/Entities/UserViewBuilder.cs
@@ -55,12 +55,12 @@ namespace MediaBrowser.Controller.Entities
             // if (query.IncludeItemTypes != null &&
             //    query.IncludeItemTypes.Length == 1 &&
             //    string.Equals(query.IncludeItemTypes[0], "Playlist", StringComparison.OrdinalIgnoreCase))
-            //{
+            // {
             //    if (!string.Equals(viewType, CollectionType.Playlists, StringComparison.OrdinalIgnoreCase))
             //    {
             //        return await FindPlaylists(queryParent, user, query).ConfigureAwait(false);
             //    }
-            //}
+            // }
 
             switch (viewType)
             {
@@ -344,12 +344,14 @@ namespace MediaBrowser.Controller.Entities
             var parentFolders = GetMediaFolders(parent, query.User, new[] { CollectionType.TvShows, string.Empty });
 
             var result = _tvSeriesManager.GetNextUp(
-            new NextUpQuery
-            {
-                Limit = query.Limit,
-                StartIndex = query.StartIndex,
-                UserId = query.User.Id
-            }, parentFolders, query.DtoOptions);
+                new NextUpQuery
+                {
+                    Limit = query.Limit,
+                    StartIndex = query.StartIndex,
+                    UserId = query.User.Id
+                },
+                parentFolders,
+                query.DtoOptions);
 
             return result;
         }
diff --git a/MediaBrowser.Controller/Entities/Video.cs b/MediaBrowser.Controller/Entities/Video.cs
index 723027a88..d05b5df2f 100644
--- a/MediaBrowser.Controller/Entities/Video.cs
+++ b/MediaBrowser.Controller/Entities/Video.cs
@@ -482,7 +482,8 @@ namespace MediaBrowser.Controller.Entities
         {
             if (!IsInMixedFolder)
             {
-                return new[] {
+                return new[]
+                {
                     new FileSystemMetadata
                     {
                         FullName = ContainingFolderPath,