Decouple Settings from MainWindow

ILSpy/Analyzers/AnalyzerTreeView.cs

@@ -44,29 +44,22 @@ namespace ICSharpCode.ILSpy.Analyzers
 	[Export]
 	public class AnalyzerTreeView : SharpTreeView
 	{
-		FilterSettings filterSettings;
-
 		public AnalyzerTreeView()
 		{
 			this.ShowRoot = false;
 			this.BorderThickness = new Thickness(0);
 			ContextMenuProvider.Add(this);
-			MessageBus<CurrentAssemblyListChangedEventArgs>.Subscribers += (sender, e) => MainWindow_Instance_CurrentAssemblyListChanged(sender, e);
+			MessageBus<CurrentAssemblyListChangedEventArgs>.Subscribers += (sender, e) => CurrentAssemblyList_Changed(sender, e);
 			MessageBus<DockWorkspaceActiveTabPageChangedEventArgs>.Subscribers += DockWorkspace_ActiveTabPageChanged;
-			filterSettings = MainWindow.Instance.SessionSettings.FilterSettings;
-			filterSettings.PropertyChanged += FilterSettings_PropertyChanged;
+			MessageBus<LanguageSettingsChangedEventArgs>.Subscribers += (sender, e) => LanguageSettings_PropertyChanged(sender, e);
 		}
 
 		private void DockWorkspace_ActiveTabPageChanged(object sender, EventArgs e)
 		{
 			this.Root ??= new AnalyzerRootNode { Language = MainWindow.Instance.CurrentLanguage };
-
-			filterSettings.PropertyChanged -= FilterSettings_PropertyChanged;
-			filterSettings = DockWorkspace.Instance.ActiveTabPage.FilterSettings;
-			filterSettings.PropertyChanged += FilterSettings_PropertyChanged;
 		}
 
-		private void FilterSettings_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
+		private void LanguageSettings_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
 		{
 			switch (e.PropertyName)
 			{
@@ -77,7 +70,7 @@ namespace ICSharpCode.ILSpy.Analyzers
 			}
 		}
 
-		void MainWindow_Instance_CurrentAssemblyListChanged(object sender, NotifyCollectionChangedEventArgs e)
+		void CurrentAssemblyList_Changed(object sender, NotifyCollectionChangedEventArgs e)
 		{
 			if (e.Action == NotifyCollectionChangedAction.Reset)
 			{

ILSpy/Commands/SetThemeCommand.cs

@@ -1,11 +1,13 @@
-namespace ICSharpCode.ILSpy.Commands
+using ICSharpCode.ILSpy.Util;
+
+namespace ICSharpCode.ILSpy.Commands
 {
 	public class SetThemeCommand : SimpleCommand
 	{
 		public override void Execute(object parameter)
 		{
 			if (parameter is string theme)
-				MainWindow.Instance.SessionSettings.Theme = theme;
+				SettingsService.Instance.SessionSettings.Theme = theme;
 		}
 	}
 }

ILSpy/LanguageSettings.cs

@@ -23,6 +23,7 @@ using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Xml.Linq;
 
+using ICSharpCode.ILSpy.Util;
 using ICSharpCode.ILSpyX;
 
 namespace ICSharpCode.ILSpy
@@ -30,12 +31,7 @@ namespace ICSharpCode.ILSpy
 	/// <summary>
 	/// Represents the filters applied to the tree view.
 	/// </summary>
-	/// <remarks>
-	/// This class is mutable; but the ILSpyTreeNode filtering assumes that filter settings are immutable.
-	/// Thus, the main window will use one mutable instance (for data-binding), and will assign a new
-	/// clone to the ILSpyTreeNodes whenever the main mutable instance changes.
-	/// </remarks>
-	public class FilterSettings : INotifyPropertyChanged
+	public class LanguageSettings : INotifyPropertyChanged
 	{
 		/// <summary>
 		/// This dictionary is necessary to remember language versions across language changes. For example, 
@@ -44,13 +40,12 @@ namespace ICSharpCode.ILSpy
 		/// </summary>
 		private readonly Dictionary<Language, LanguageVersion> languageVersionHistory = new Dictionary<Language, LanguageVersion>();
 
-		public FilterSettings(XElement element)
+		public LanguageSettings(XElement element)
 		{
 			this.ShowApiLevel = (ApiVisibility?)(int?)element.Element("ShowAPILevel") ?? ApiVisibility.PublicAndInternal;
 			this.Language = Languages.GetLanguage((string)element.Element("Language"));
-			this.LanguageVersion = Language.LanguageVersions.FirstOrDefault(v => v.Version == (string)element.Element("LanguageVersion"));
-			if (this.LanguageVersion == default(LanguageVersion))
-				this.LanguageVersion = language.LanguageVersions.LastOrDefault();
+			this.LanguageVersion = Language.LanguageVersions.FirstOrDefault(v => v.Version == (string)element.Element("LanguageVersion"))
+								   ?? Language.LanguageVersions.LastOrDefault();
 		}
 
 		public XElement SaveAsXml()
@@ -63,33 +58,6 @@ namespace ICSharpCode.ILSpy
 			);
 		}
 
-		string searchTerm;
-
-		/// <summary>
-		/// Gets/Sets the search term.
-		/// Only tree nodes containing the search term will be shown.
-		/// </summary>
-		public string SearchTerm {
-			get { return searchTerm; }
-			set {
-				if (searchTerm != value)
-				{
-					searchTerm = value;
-					OnPropertyChanged(nameof(SearchTerm));
-				}
-			}
-		}
-
-		/// <summary>
-		/// Gets whether a node with the specified text is matched by the current search term.
-		/// </summary>
-		public virtual bool SearchTermMatches(string text)
-		{
-			if (string.IsNullOrEmpty(searchTerm))
-				return true;
-			return text.IndexOf(searchTerm, StringComparison.OrdinalIgnoreCase) >= 0;
-		}
-
 		ApiVisibility showApiLevel;
 
 		/// <summary>
@@ -211,15 +179,23 @@ namespace ICSharpCode.ILSpy
 		{
 			if (PropertyChanged != null)
 			{
-				PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
+				var args = new PropertyChangedEventArgs(propertyName);
+
+				PropertyChanged(this, args);
+				MessageBus.Send(this, new LanguageSettingsChangedEventArgs(args));
 			}
 		}
 
-		public FilterSettings Clone()
+
+		// This class has been initially called FilterSettings, but then has been Hijacked to store language settings as well.
+		// While the filter settings were some sort of local, the language settings are global. This is a bit of a mess.
+		// There has been a lot of workarounds cloning the FilterSettings to pass them down to the tree nodes, without messing up the global language settings.
+		// Finally, this filtering was not used at all, so this SearchTerm is just a placeholder to make the filtering code compile, in case someone wants to reactivate filtering in the future.
+		public string SearchTerm => string.Empty;
+
+		public bool SearchTermMatches(string value)
 		{
-			FilterSettings f = (FilterSettings)MemberwiseClone();
-			f.PropertyChanged = null;
-			return f;
+			return true;
 		}
 	}
 }

ILSpy/MainWindow.xaml

@@ -123,9 +123,9 @@
 			<MenuItem Header="{x:Static properties:Resources._File}" Tag="_File" />
 			<!-- contents of file menu are added using MEF -->
 			<MenuItem Header="{x:Static properties:Resources._View}" Tag="_View">
-				<MenuItem Header="{x:Static properties:Resources.Show_publiconlyTypesMembers}" IsCheckable="True" IsChecked="{Binding Workspace.ActiveTabPage.FilterSettings.ApiVisPublicOnly}" />
-				<MenuItem Header="{x:Static properties:Resources.Show_internalTypesMembers}" IsCheckable="True" IsChecked="{Binding Workspace.ActiveTabPage.FilterSettings.ApiVisPublicAndInternal}" />
-				<MenuItem Header="{x:Static properties:Resources.Show_allTypesAndMembers}" IsCheckable="True" IsChecked="{Binding Workspace.ActiveTabPage.FilterSettings.ApiVisAll}" />
+				<MenuItem Header="{x:Static properties:Resources.Show_publiconlyTypesMembers}" IsCheckable="True" IsChecked="{Binding SessionSettings.LanguageSettings.ApiVisPublicOnly}" />
+				<MenuItem Header="{x:Static properties:Resources.Show_internalTypesMembers}" IsCheckable="True" IsChecked="{Binding SessionSettings.LanguageSettings.ApiVisPublicAndInternal}" />
+				<MenuItem Header="{x:Static properties:Resources.Show_allTypesAndMembers}" IsCheckable="True" IsChecked="{Binding SessionSettings.LanguageSettings.ApiVisAll}" />
 				<Separator/>
 				<MenuItem Header="{x:Static properties:Resources.Theme}" ItemsSource="{x:Static themes:ThemeManager.AllThemes}">
 					<MenuItem.ItemContainerStyle>
@@ -189,25 +189,25 @@
 				<Image Width="16" Height="16" Source="{controls:XamlResource Images/AssemblyList}" Style="{StaticResource DarkModeAwareImageStyle}"/>
 			</Button>
 			<Separator />
-			<CheckBox IsChecked="{Binding Workspace.ActiveTabPage.FilterSettings.ApiVisPublicOnly}" ToolTip="{x:Static properties:Resources.ShowPublicOnlyTypesMembers}">
+			<CheckBox IsChecked="{Binding SessionSettings.LanguageSettings.ApiVisPublicOnly}" ToolTip="{x:Static properties:Resources.ShowPublicOnlyTypesMembers}">
 				<Image Width="16" Height="16" Source="{controls:XamlResource Images/ShowPublicOnly}" Style="{StaticResource DarkModeAwareImageStyle}"/>
 			</CheckBox>
-			<CheckBox IsChecked="{Binding Workspace.ActiveTabPage.FilterSettings.ApiVisPublicAndInternal}" ToolTip="{x:Static properties:Resources.ShowInternalTypesMembers}">
+			<CheckBox IsChecked="{Binding SessionSettings.LanguageSettings.ApiVisPublicAndInternal}" ToolTip="{x:Static properties:Resources.ShowInternalTypesMembers}">
 				<Image Width="16" Height="16" Source="{controls:XamlResource Images/ShowPrivateInternal}" Style="{StaticResource DarkModeAwareImageStyle}"/>
 			</CheckBox>
-			<CheckBox IsChecked="{Binding Workspace.ActiveTabPage.FilterSettings.ApiVisAll}" ToolTip="{x:Static properties:Resources.ShowAllTypesAndMembers}">
+			<CheckBox IsChecked="{Binding SessionSettings.LanguageSettings.ApiVisAll}" ToolTip="{x:Static properties:Resources.ShowAllTypesAndMembers}">
 				<Image Width="16" Height="16" Source="{controls:XamlResource Images/ShowAll}" Style="{StaticResource DarkModeAwareImageStyle}"/>
 			</CheckBox>
 			<Separator />
 			<ComboBox Name="languageComboBox" DisplayMemberPath="Name" Width="100" MaxDropDownHeight="Auto"
 					  IsEnabled="{Binding Workspace.ActiveTabPage.SupportsLanguageSwitching}"
 			          ItemsSource="{x:Static local:Languages.AllLanguages}" ToolTip="{x:Static properties:Resources.SelectLanguageDropdownTooltip}"
-			          SelectedItem="{Binding Workspace.ActiveTabPage.FilterSettings.Language}"/>
+			          SelectedItem="{Binding SessionSettings.LanguageSettings.Language}"/>
 			<ComboBox Name="languageVersionComboBox" DisplayMemberPath="DisplayName" Width="120" MaxDropDownHeight="Auto" ToolTip="{x:Static properties:Resources.SelectVersionDropdownTooltip}"
 			          Visibility="{Binding SelectedItem.HasLanguageVersions, ElementName=languageComboBox, Converter={toms:BooleanToVisibilityConverter}}"
 					  IsEnabled="{Binding Workspace.ActiveTabPage.SupportsLanguageSwitching}"
 			          ItemsSource="{Binding SelectedItem.LanguageVersions, ElementName=languageComboBox, UpdateSourceTrigger=PropertyChanged}"
-			          SelectedItem="{Binding Workspace.ActiveTabPage.FilterSettings.LanguageVersion, UpdateSourceTrigger=PropertyChanged}"/>
+			          SelectedItem="{Binding SessionSettings.LanguageSettings.LanguageVersion, UpdateSourceTrigger=PropertyChanged}"/>
 		</ToolBar>
 		<!-- Update panel -->
 		<Border DockPanel.Dock="Top" BorderBrush="Black" BorderThickness="1" Name="updatePanel" Visibility="Collapsed">

ILSpy/MainWindow.xaml.cs

@@ -73,9 +73,7 @@ namespace ICSharpCode.ILSpy
 	{
 		bool refreshInProgress, changingActiveTab;
 		readonly NavigationHistory<NavigationState> history = new NavigationHistory<NavigationState>();
-		ILSpySettings spySettingsForMainWindow_Loaded;
-		SessionSettings sessionSettings;
-		FilterSettings filterSettings;
+
 		AssemblyList assemblyList;
 		AssemblyListTreeNode assemblyListTreeNode;
 
@@ -85,10 +83,6 @@ namespace ICSharpCode.ILSpy
 			get { return instance; }
 		}
 
-		public SessionSettings SessionSettings {
-			get { return sessionSettings; }
-		}
-
 		internal AssemblyListManager AssemblyListManager { get; }
 
 		public SharpTreeView AssemblyTreeView {
@@ -116,9 +110,10 @@ namespace ICSharpCode.ILSpy
 		public MainWindow()
 		{
 			instance = this;
-			var spySettings = ILSpySettings.Load();
-			this.spySettingsForMainWindow_Loaded = spySettings;
-			this.sessionSettings = new SessionSettings(spySettings);
+
+			var spySettings = SettingsService.Instance.SpySettings;
+			var sessionSettings = SettingsService.Instance.SessionSettings;
+
 			this.CurrentDecompilerSettings = DecompilerSettingsPanel.LoadDecompilerSettings(spySettings);
 			this.CurrentDisplaySettings = DisplaySettingsPanel.LoadDisplaySettings(spySettings);
 			this.AssemblyListManager = new AssemblyListManager(spySettings) {
@@ -144,10 +139,11 @@ namespace ICSharpCode.ILSpy
 			InitializeComponent();
 			InitToolPanes();
 			DockWorkspace.Instance.InitializeLayout(DockManager);
-			sessionSettings.PropertyChanged += SessionSettings_PropertyChanged;
-			filterSettings = sessionSettings.FilterSettings;
-			filterSettings.PropertyChanged += filterSettings_PropertyChanged;
+
+			MessageBus<SessionSettingsChangedEventArgs>.Subscribers += (sender, e) => SessionSettings_PropertyChanged(sender, e);
+			MessageBus<LanguageSettingsChangedEventArgs>.Subscribers += (sender, e) => filterSettings_PropertyChanged(sender, e);
 			MessageBus<DockWorkspaceActiveTabPageChangedEventArgs>.Subscribers += DockWorkspace_ActiveTabPageChanged;
+
 			InitMainMenu();
 			InitWindowMenu();
 			InitToolbar();
@@ -160,9 +156,6 @@ namespace ICSharpCode.ILSpy
 		private void DockWorkspace_ActiveTabPageChanged(object sender, EventArgs e)
 		{
 			DockWorkspace dock = DockWorkspace.Instance;
-			filterSettings.PropertyChanged -= filterSettings_PropertyChanged;
-			filterSettings = dock.ActiveTabPage.FilterSettings;
-			filterSettings.PropertyChanged += filterSettings_PropertyChanged;
 
 			var windowMenuItem = mainMenu.Items.OfType<MenuItem>().First(m => (string)m.Tag == nameof(Properties.Resources._Window));
 			foreach (MenuItem menuItem in windowMenuItem.Items.OfType<MenuItem>())
@@ -176,6 +169,8 @@ namespace ICSharpCode.ILSpy
 
 		private void SessionSettings_PropertyChanged(object sender, PropertyChangedEventArgs e)
 		{
+			var sessionSettings = SettingsService.Instance.SessionSettings;
+
 			switch (e.PropertyName)
 			{
 				case nameof(SessionSettings.ActiveAssemblyList):
@@ -580,6 +575,8 @@ namespace ICSharpCode.ILSpy
 			base.OnSourceInitialized(e);
 			PresentationSource source = PresentationSource.FromVisual(this);
 
+			var sessionSettings = SettingsService.Instance.SessionSettings;
+
 			// Validate and Set Window Bounds
 			Rect bounds = Rect.Transform(sessionSettings.WindowBounds, source.CompositionTarget.TransformToDevice);
 			var boundsRect = new System.Drawing.Rectangle((int)bounds.Left, (int)bounds.Top, (int)bounds.Width, (int)bounds.Height);
@@ -648,7 +645,7 @@ namespace ICSharpCode.ILSpy
 		{
 			LoadAssemblies(args.AssembliesToLoad, commandLineLoadedAssemblies, focusNode: false);
 			if (args.Language != null)
-				filterSettings.Language = Languages.GetLanguage(args.Language);
+				SettingsService.Instance.SessionSettings.LanguageSettings.Language = Languages.GetLanguage(args.Language);
 			return true;
 		}
 
@@ -658,6 +655,8 @@ namespace ICSharpCode.ILSpy
 		/// </summary>
 		void HandleCommandLineArgumentsAfterShowList(CommandLineArguments args, ILSpySettings spySettings = null)
 		{
+			var sessionSettings = SettingsService.Instance.SessionSettings;
+
 			var relevantAssemblies = commandLineLoadedAssemblies.ToList();
 			commandLineLoadedAssemblies.Clear(); // clear references once we don't need them anymore
 			NavigateOnLaunch(args.NavigateTo, sessionSettings.ActiveTreeViewPath, spySettings, relevantAssemblies);
@@ -832,15 +831,13 @@ namespace ICSharpCode.ILSpy
 
 		void MainWindow_Loaded(object sender, RoutedEventArgs e)
 		{
-			DockWorkspace.Instance.TabPages.Add(new TabPageModel() {
-				FilterSettings = filterSettings.Clone()
-			});
+			DockWorkspace.Instance.TabPages.Add(new() { });
 			DockWorkspace.Instance.ActiveTabPage = DockWorkspace.Instance.TabPages.First();
 
-			ILSpySettings spySettings = this.spySettingsForMainWindow_Loaded;
-			this.spySettingsForMainWindow_Loaded = null;
 			var loadPreviousAssemblies = Options.MiscSettingsPanel.CurrentMiscSettings.LoadPreviousAssemblies;
 
+			var sessionSettings = SettingsService.Instance.SessionSettings;
+
 			if (loadPreviousAssemblies)
 			{
 				// Load AssemblyList only in Loaded event so that WPF is initialized before we start the CPU-heavy stuff.
@@ -870,7 +867,7 @@ namespace ICSharpCode.ILSpy
 				this.assemblyList.Open(sessionSettings.ActiveAutoLoadedAssembly, true);
 			}
 
-			Dispatcher.BeginInvoke(DispatcherPriority.Loaded, new Action(() => OpenAssemblies(spySettings)));
+			Dispatcher.BeginInvoke(DispatcherPriority.Loaded, new Action(() => OpenAssemblies(SettingsService.Instance.SpySettings)));
 		}
 
 		void OpenAssemblies(ILSpySettings spySettings)
@@ -1000,7 +997,6 @@ namespace ICSharpCode.ILSpy
 			assemblyList.CollectionChanged += assemblyList_Assemblies_CollectionChanged;
 
 			assemblyListTreeNode = new AssemblyListTreeNode(assemblyList);
-			assemblyListTreeNode.FilterSettings = filterSettings.Clone();
 			assemblyListTreeNode.Select = x => SelectNode(x, inNewTabPage: false);
 			AssemblyTreeView.Root = assemblyListTreeNode;
 
@@ -1064,13 +1060,7 @@ namespace ICSharpCode.ILSpy
 
 		public void RefreshTreeViewFilter()
 		{
-			// filterSettings is mutable; but the ILSpyTreeNode filtering assumes that filter settings are immutable.
-			// Thus, the main window will use one mutable instance (for data-binding), and assign a new clone to the ILSpyTreeNodes whenever the main
-			// mutable instance changes.
-			FilterSettings filterSettings = DockWorkspace.Instance.ActiveTabPage.FilterSettings.Clone();
-			if (assemblyListTreeNode != null)
-				assemblyListTreeNode.FilterSettings = filterSettings;
-			SearchPane.UpdateFilter(filterSettings);
+			SearchPane.UpdateFilter();
 		}
 
 		internal AssemblyListTreeNode AssemblyListTreeNode {
@@ -1097,10 +1087,7 @@ namespace ICSharpCode.ILSpy
 				{
 					if (inNewTabPage)
 					{
-						DockWorkspace.Instance.TabPages.Add(
-							new TabPageModel() {
-								FilterSettings = filterSettings.Clone()
-							});
+						DockWorkspace.Instance.TabPages.Add(new TabPageModel() { });
 						DockWorkspace.Instance.ActiveTabPage = DockWorkspace.Instance.TabPages.Last();
 						AssemblyTreeView.SelectedItem = null;
 					}
@@ -1143,10 +1130,7 @@ namespace ICSharpCode.ILSpy
 		{
 			if (inNewTabPage)
 			{
-				DockWorkspace.Instance.TabPages.Add(
-					new TabPageModel() {
-						FilterSettings = filterSettings.Clone()
-					});
+				DockWorkspace.Instance.TabPages.Add(new TabPageModel() { });
 				DockWorkspace.Instance.ActiveTabPage = DockWorkspace.Instance.TabPages.Last();
 			}
 
@@ -1519,8 +1503,9 @@ namespace ICSharpCode.ILSpy
 			}
 		}
 
-		public Language CurrentLanguage => DockWorkspace.Instance.ActiveTabPage.FilterSettings.Language;
-		public LanguageVersion CurrentLanguageVersion => DockWorkspace.Instance.ActiveTabPage.FilterSettings.LanguageVersion;
+		public Language CurrentLanguage => SettingsService.Instance.SessionSettings.LanguageSettings.Language;
+
+		public LanguageVersion CurrentLanguageVersion => SettingsService.Instance.SessionSettings.LanguageSettings.LanguageVersion;
 
 		public event SelectionChangedEventHandler SelectionChanged;
 
@@ -1590,10 +1575,7 @@ namespace ICSharpCode.ILSpy
 			{
 				if (inNewTabPage)
 				{
-					DockWorkspace.Instance.TabPages.Add(
-						new TabPageModel() {
-							FilterSettings = filterSettings.Clone()
-						});
+					DockWorkspace.Instance.TabPages.Add(new() { });
 					DockWorkspace.Instance.ActiveTabPage = DockWorkspace.Instance.TabPages.Last();
 				}
 
@@ -1646,18 +1628,19 @@ namespace ICSharpCode.ILSpy
 			base.OnStateChanged(e);
 			// store window state in settings only if it's not minimized
 			if (this.WindowState != System.Windows.WindowState.Minimized)
-				sessionSettings.WindowState = this.WindowState;
+				SettingsService.Instance.SessionSettings.WindowState = this.WindowState;
 		}
 
 		protected override void OnClosing(CancelEventArgs e)
 		{
 			base.OnClosing(e);
+			var sessionSettings = SettingsService.Instance.SessionSettings;
+
 			sessionSettings.ActiveAssemblyList = assemblyList.ListName;
 			sessionSettings.ActiveTreeViewPath = GetPathForNode(AssemblyTreeView.SelectedItem as SharpTreeNode);
 			sessionSettings.ActiveAutoLoadedAssembly = GetAutoLoadedAssemblyNode(AssemblyTreeView.SelectedItem as SharpTreeNode);
 			sessionSettings.WindowBounds = this.RestoreBounds;
 			sessionSettings.DockLayout.Serialize(new XmlLayoutSerializer(DockManager));
-			sessionSettings.FilterSettings = DockWorkspace.Instance.ActiveTabPage.FilterSettings.Clone();
 			sessionSettings.Save();
 		}
 

ILSpy/Options/DisplaySettingsPanel.xaml.cs

@@ -27,6 +27,7 @@ using System.Windows.Media;
 using System.Windows.Threading;
 using System.Xml.Linq;
 
+using ICSharpCode.ILSpy.Util;
 using ICSharpCode.ILSpyX.Settings;
 
 namespace ICSharpCode.ILSpy.Options
@@ -123,7 +124,7 @@ namespace ICSharpCode.ILSpy.Options
 			s.ShowRawOffsetsAndBytesBeforeInstruction = (bool?)e.Attribute("ShowRawOffsetsAndBytesBeforeInstruction") ?? false;
 			s.StyleWindowTitleBar = (bool?)e.Attribute("StyleWindowTitleBar") ?? false;
 
-			s.Theme = MainWindow.Instance.SessionSettings.Theme;
+			s.Theme = SettingsService.Instance.SessionSettings.Theme;
 
 			return s;
 		}
@@ -154,8 +155,8 @@ namespace ICSharpCode.ILSpy.Options
 			section.SetAttributeValue("ShowRawOffsetsAndBytesBeforeInstruction", s.ShowRawOffsetsAndBytesBeforeInstruction);
 			section.SetAttributeValue("StyleWindowTitleBar", s.StyleWindowTitleBar);
 
-			MainWindow.Instance.SessionSettings.Theme = s.Theme;
-			var sessionSettings = MainWindow.Instance.SessionSettings.ToXml();
+			SettingsService.Instance.SessionSettings.Theme = s.Theme;
+			var sessionSettings = SettingsService.Instance.SessionSettings.ToXml();
 
 			MainWindow.Instance.CurrentDisplaySettings.CopyValues(s);
 

ILSpy/Search/SearchPane.cs

@@ -50,6 +50,7 @@ namespace ICSharpCode.ILSpy.Search
 	/// </summary>
 	[DataTemplate(typeof(SearchPaneModel))]
 	[PartCreationPolicy(CreationPolicy.Shared)]
+	[Export]
 	public partial class SearchPane : UserControl
 	{
 		const int MAX_RESULTS = 1000;
@@ -57,7 +58,6 @@ namespace ICSharpCode.ILSpy.Search
 		RunningSearch currentSearch;
 		bool runSearchOnNextShow;
 		IComparer<SearchResult> resultsComparer;
-		FilterSettings filterSettings;
 
 		public static readonly DependencyProperty ResultsProperty =
 			DependencyProperty.Register("Results", typeof(ObservableCollection<SearchResult>), typeof(SearchPane),
@@ -84,11 +84,10 @@ namespace ICSharpCode.ILSpy.Search
 
 			ContextMenuProvider.Add(listBox);
 			MessageBus<CurrentAssemblyListChangedEventArgs>.Subscribers += (sender, e) => MainWindow_Instance_CurrentAssemblyListChanged(sender, e);
-			filterSettings = MainWindow.Instance.SessionSettings.FilterSettings;
 			CompositionTarget.Rendering += UpdateResults;
 
 			// This starts empty search right away, so do at the end (we're still in ctor)
-			searchModeComboBox.SelectedIndex = (int)MainWindow.Instance.SessionSettings.SelectedSearchMode;
+			searchModeComboBox.SelectedIndex = (int)SettingsService.Instance.SessionSettings.SelectedSearchMode;
 		}
 
 		void MainWindow_Instance_CurrentAssemblyListChanged(object sender, NotifyCollectionChangedEventArgs e)
@@ -104,10 +103,8 @@ namespace ICSharpCode.ILSpy.Search
 			}
 		}
 
-		internal void UpdateFilter(FilterSettings settings)
+		internal void UpdateFilter()
 		{
-			this.filterSettings = settings;
-
 			if (IsVisible)
 			{
 				StartSearch(this.SearchTerm);
@@ -155,7 +152,7 @@ namespace ICSharpCode.ILSpy.Search
 
 		void SearchModeComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
 		{
-			MainWindow.Instance.SessionSettings.SelectedSearchMode = (SearchMode)searchModeComboBox.SelectedIndex;
+			SettingsService.Instance.SessionSettings.SelectedSearchMode = (SearchMode)searchModeComboBox.SelectedIndex;
 			StartSearch(this.SearchTerm);
 		}
 
@@ -258,7 +255,7 @@ namespace ICSharpCode.ILSpy.Search
 				searchProgressBar.IsIndeterminate = true;
 				startedSearch = new RunningSearch(await mainWindow.CurrentAssemblyList.GetAllAssemblies(), searchTerm,
 					(SearchMode)searchModeComboBox.SelectedIndex, mainWindow.CurrentLanguage,
-					filterSettings.ShowApiLevel);
+					SettingsService.Instance.SessionSettings.LanguageSettings.ShowApiLevel);
 				currentSearch = startedSearch;
 
 				await startedSearch.Run();

ILSpy/SessionSettings.cs

@@ -28,6 +28,7 @@ using System.Xml.Linq;
 
 using ICSharpCode.ILSpy.Docking;
 using ICSharpCode.ILSpy.Themes;
+using ICSharpCode.ILSpy.Util;
 using ICSharpCode.ILSpyX.Search;
 using ICSharpCode.ILSpyX.Settings;
 
@@ -47,7 +48,7 @@ namespace ICSharpCode.ILSpy
 			if (filterSettings == null)
 				filterSettings = new XElement("FilterSettings");
 
-			this.FilterSettings = new FilterSettings(filterSettings);
+			this.LanguageSettings = new LanguageSettings(filterSettings);
 
 			this.ActiveAssemblyList = (string)doc.Element("ActiveAssemblyList");
 
@@ -72,10 +73,15 @@ namespace ICSharpCode.ILSpy
 
 		void OnPropertyChanged([CallerMemberName] string propertyName = null)
 		{
-			PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
+			var args = new PropertyChangedEventArgs(propertyName);
+
+			PropertyChanged?.Invoke(this, args);
+
+			MessageBus.Send(this, new SessionSettingsChangedEventArgs(args));
 		}
 
-		public FilterSettings FilterSettings { get; internal set; }
+		public LanguageSettings LanguageSettings { get; }
+
 		public SearchMode SelectedSearchMode { get; set; }
 
 		public string Theme {
@@ -113,16 +119,16 @@ namespace ICSharpCode.ILSpy
 			}
 		}
 
-		public WindowState WindowState = WindowState.Normal;
+		public WindowState WindowState;
 		public Rect WindowBounds;
 		internal static Rect DefaultWindowBounds = new Rect(10, 10, 750, 550);
 
-		public DockLayoutSettings DockLayout { get; private set; }
+		public DockLayoutSettings DockLayout { get; }
 
 		public XElement ToXml()
 		{
 			XElement doc = new XElement("SessionSettings");
-			doc.Add(this.FilterSettings.SaveAsXml());
+			doc.Add(this.LanguageSettings.SaveAsXml());
 			if (this.ActiveAssemblyList != null)
 			{
 				doc.Add(new XElement("ActiveAssemblyList", this.ActiveAssemblyList));

ILSpy/TreeNodes/AssemblyTreeNode.cs

@@ -449,7 +449,7 @@ namespace ICSharpCode.ILSpy.TreeNodes
 			return dataObject;
 		}
 
-		public override FilterResult Filter(FilterSettings settings)
+		public override FilterResult Filter(LanguageSettings settings)
 		{
 			if (settings.SearchTermMatches(LoadedAssembly.ShortName))
 				return FilterResult.Match;

ILSpy/TreeNodes/DerivedTypesEntryNode.cs

@@ -50,7 +50,7 @@ namespace ICSharpCode.ILSpy.TreeNodes
 
 		public override object Icon => TypeTreeNode.GetIcon(type);
 
-		public override FilterResult Filter(FilterSettings settings)
+		public override FilterResult Filter(LanguageSettings settings)
 		{
 			if (settings.ShowApiLevel == ApiVisibility.PublicOnly && !IsPublicAPI)
 				return FilterResult.Hidden;

ILSpy/TreeNodes/EventTreeNode.cs

@@ -68,7 +68,7 @@ namespace ICSharpCode.ILSpy.TreeNodes
 			return Images.GetIcon(MemberIcon.Event, MethodTreeNode.GetOverlayIcon(@event.Accessibility), @event.IsStatic);
 		}
 
-		public override FilterResult Filter(FilterSettings settings)
+		public override FilterResult Filter(LanguageSettings settings)
 		{
 			if (settings.ShowApiLevel == ApiVisibility.PublicOnly && !IsPublicAPI)
 				return FilterResult.Hidden;

ILSpy/TreeNodes/FieldTreeNode.cs

@@ -69,7 +69,7 @@ namespace ICSharpCode.ILSpy.TreeNodes
 			return Images.GetIcon(MemberIcon.Field, MethodTreeNode.GetOverlayIcon(field.Accessibility), field.IsStatic);
 		}
 
-		public override FilterResult Filter(FilterSettings settings)
+		public override FilterResult Filter(LanguageSettings settings)
 		{
 			if (settings.ShowApiLevel == ApiVisibility.PublicOnly && !IsPublicAPI)
 				return FilterResult.Hidden;

ILSpy/TreeNodes/ILSpyTreeNode.cs

@@ -27,6 +27,7 @@ using System.Windows.Threading;
 
 using ICSharpCode.Decompiler;
 using ICSharpCode.Decompiler.TypeSystem;
+using ICSharpCode.ILSpy.Util;
 using ICSharpCode.ILSpyX.Abstractions;
 using ICSharpCode.ILSpyX.TreeView.PlatformAbstractions;
 using ICSharpCode.ILSpyX.TreeView;
@@ -38,25 +39,20 @@ namespace ICSharpCode.ILSpy.TreeNodes
 	/// </summary>
 	public abstract class ILSpyTreeNode : SharpTreeNode, ITreeNode
 	{
-		FilterSettings filterSettings;
 		bool childrenNeedFiltering;
 
-		public FilterSettings FilterSettings {
-			get { return filterSettings; }
-			set {
-				if (filterSettings != value)
-				{
-					filterSettings = value;
-					OnFilterSettingsChanged();
-				}
-			}
+		public ILSpyTreeNode()
+		{
+			MessageBus<LanguageSettingsChangedEventArgs>.Subscribers += LanguageSettings_Changed;
 		}
 
+		LanguageSettings LanguageSettings => SettingsService.Instance.SessionSettings.LanguageSettings;
+
 		public Language Language {
-			get { return filterSettings != null ? filterSettings.Language : Languages.AllLanguages[0]; }
+			get { return LanguageSettings.Language ?? Languages.AllLanguages[0]; }
 		}
 
-		public virtual FilterResult Filter(FilterSettings settings)
+		public virtual FilterResult Filter(LanguageSettings settings)
 		{
 			if (string.IsNullOrEmpty(settings.SearchTerm))
 				return FilterResult.Match;
@@ -92,7 +88,7 @@ namespace ICSharpCode.ILSpy.TreeNodes
 			return false;
 		}
 
-		internal protected override void OnChildrenChanged(NotifyCollectionChangedEventArgs e)
+		protected internal override void OnChildrenChanged(NotifyCollectionChangedEventArgs e)
 		{
 			if (e.NewItems != null)
 			{
@@ -111,27 +107,21 @@ namespace ICSharpCode.ILSpy.TreeNodes
 
 		void ApplyFilterToChild(ILSpyTreeNode child)
 		{
-			FilterResult r;
-			if (this.FilterSettings == null)
-				r = FilterResult.Match;
-			else
-				r = child.Filter(this.FilterSettings);
+			FilterResult r = child.Filter(this.LanguageSettings);
+
 			switch (r)
 			{
 				case FilterResult.Hidden:
 					child.IsHidden = true;
 					break;
 				case FilterResult.Match:
-					child.FilterSettings = StripSearchTerm(this.FilterSettings);
 					child.IsHidden = false;
 					break;
 				case FilterResult.Recurse:
-					child.FilterSettings = this.FilterSettings;
 					child.EnsureChildrenFiltered();
 					child.IsHidden = child.Children.All(c => c.IsHidden);
 					break;
 				case FilterResult.MatchAndRecurse:
-					child.FilterSettings = StripSearchTerm(this.FilterSettings);
 					child.EnsureChildrenFiltered();
 					child.IsHidden = child.Children.All(c => c.IsHidden);
 					break;
@@ -140,19 +130,7 @@ namespace ICSharpCode.ILSpy.TreeNodes
 			}
 		}
 
-		static FilterSettings StripSearchTerm(FilterSettings filterSettings)
-		{
-			if (filterSettings == null)
-				return null;
-			if (!string.IsNullOrEmpty(filterSettings.SearchTerm))
-			{
-				filterSettings = filterSettings.Clone();
-				filterSettings.SearchTerm = null;
-			}
-			return filterSettings;
-		}
-
-		protected virtual void OnFilterSettingsChanged()
+		protected virtual void LanguageSettings_Changed(object sender, EventArgs e)
 		{
 			RaisePropertyChanged(nameof(Text));
 			if (IsVisible)
@@ -166,11 +144,6 @@ namespace ICSharpCode.ILSpy.TreeNodes
 			}
 		}
 
-		/*protected override void OnIsVisibleChanged()
-		{
-			base.OnIsVisibleChanged();
-			EnsureChildrenFiltered();
-		}*/
 
 		internal void EnsureChildrenFiltered()
 		{

ILSpy/TreeNodes/MethodTreeNode.cs

@@ -99,7 +99,7 @@ namespace ICSharpCode.ILSpy.TreeNodes
 			language.DecompileMethod(MethodDefinition, output, options);
 		}
 
-		public override FilterResult Filter(FilterSettings settings)
+		public override FilterResult Filter(LanguageSettings settings)
 		{
 			if (settings.ShowApiLevel == ApiVisibility.PublicOnly && !IsPublicAPI)
 				return FilterResult.Hidden;

ILSpy/TreeNodes/NamespaceTreeNode.cs

@@ -57,7 +57,7 @@ namespace ICSharpCode.ILSpy.TreeNodes
 			this.isPublicAPI = value;
 		}
 
-		public override FilterResult Filter(FilterSettings settings)
+		public override FilterResult Filter(LanguageSettings settings)
 		{
 			if (settings.SearchTermMatches(name))
 				return FilterResult.MatchAndRecurse;

ILSpy/TreeNodes/PropertyTreeNode.cs

@@ -71,7 +71,7 @@ namespace ICSharpCode.ILSpy.TreeNodes
 				MethodTreeNode.GetOverlayIcon(property.Accessibility), property.IsStatic);
 		}
 
-		public override FilterResult Filter(FilterSettings settings)
+		public override FilterResult Filter(LanguageSettings settings)
 		{
 			if (settings.ShowApiLevel == ApiVisibility.PublicOnly && !IsPublicAPI)
 				return FilterResult.Hidden;

ILSpy/TreeNodes/ResourceListTreeNode.cs

@@ -51,7 +51,7 @@ namespace ICSharpCode.ILSpy.TreeNodes
 				this.Children.Add(ResourceTreeNode.Create(r));
 		}
 
-		public override FilterResult Filter(FilterSettings settings)
+		public override FilterResult Filter(LanguageSettings settings)
 		{
 			if (string.IsNullOrEmpty(settings.SearchTerm))
 				return FilterResult.MatchAndRecurse;

ILSpy/TreeNodes/ResourceNodes/ResourceTreeNode.cs

@@ -55,7 +55,7 @@ namespace ICSharpCode.ILSpy.TreeNodes
 
 		public override object Icon => Images.Resource;
 
-		public override FilterResult Filter(FilterSettings settings)
+		public override FilterResult Filter(LanguageSettings settings)
 		{
 			if (settings.ShowApiLevel == ApiVisibility.PublicOnly && (Resource.Attributes & ManifestResourceAttributes.VisibilityMask) == ManifestResourceAttributes.Private)
 				return FilterResult.Hidden;

ILSpy/TreeNodes/ThreadingSupport.cs

@@ -138,7 +138,7 @@ namespace ICSharpCode.ILSpy.TreeNodes
 				get { return Resources.Loading; }
 			}
 
-			public override FilterResult Filter(FilterSettings settings)
+			public override FilterResult Filter(LanguageSettings settings)
 			{
 				return FilterResult.Match;
 			}
@@ -161,7 +161,7 @@ namespace ICSharpCode.ILSpy.TreeNodes
 				this.text = text;
 			}
 
-			public override FilterResult Filter(FilterSettings settings)
+			public override FilterResult Filter(LanguageSettings settings)
 			{
 				return FilterResult.Match;
 			}

ILSpy/TreeNodes/TypeTreeNode.cs

@@ -67,7 +67,7 @@ namespace ICSharpCode.ILSpy.TreeNodes
 			}
 		}
 
-		public override FilterResult Filter(FilterSettings settings)
+		public override FilterResult Filter(LanguageSettings settings)
 		{
 			if (settings.ShowApiLevel == ApiVisibility.PublicOnly && !IsPublicAPI)
 				return FilterResult.Hidden;

ILSpy/Util/MessageBus.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Specialized;
+using System.ComponentModel;
 
 using TomsToolbox.Essentials;
 
@@ -51,5 +52,9 @@ namespace ICSharpCode.ILSpy.Util
 
 	public class CurrentAssemblyListChangedEventArgs(NotifyCollectionChangedEventArgs e) : WrappedEventArgs<NotifyCollectionChangedEventArgs>(e);
 
+	public class LanguageSettingsChangedEventArgs(PropertyChangedEventArgs e) : WrappedEventArgs<PropertyChangedEventArgs>(e);
+
+	public class SessionSettingsChangedEventArgs(PropertyChangedEventArgs e) : WrappedEventArgs<PropertyChangedEventArgs>(e);
+
 	public class DockWorkspaceActiveTabPageChangedEventArgs : EventArgs;
 }

ILSpy/Util/SettingsService.cs

@@ -0,0 +1,20 @@
+using ICSharpCode.ILSpyX.Settings;
+
+namespace ICSharpCode.ILSpy.Util
+{
+	internal class SettingsService
+	{
+		public static readonly SettingsService Instance = new SettingsService();
+
+		private SettingsService()
+		{
+			this.SpySettings = ILSpySettings.Load();
+
+			SessionSettings = new(this.SpySettings);
+		}
+
+		public ILSpySettings SpySettings { get; }
+
+		public SessionSettings SessionSettings { get; }
+	}
+}

ILSpy/ViewModels/ManageAssemblyListsViewModel.cs

@@ -27,6 +27,7 @@ using System.Windows.Input;
 using ICSharpCode.Decompiler.Metadata;
 using ICSharpCode.ILSpy.Commands;
 using ICSharpCode.ILSpy.Properties;
+using ICSharpCode.ILSpy.Util;
 using ICSharpCode.ILSpyX;
 
 namespace ICSharpCode.ILSpy.ViewModels
@@ -174,7 +175,7 @@ namespace ICSharpCode.ILSpy.ViewModels
 				return;
 			manager.ClearAll();
 			manager.CreateDefaultAssemblyLists();
-			MainWindow.Instance.SessionSettings.ActiveAssemblyList = manager.AssemblyLists[0];
+			SettingsService.Instance.SessionSettings.ActiveAssemblyList = manager.AssemblyLists[0];
 		}
 
 		private void ExecuteDelete()
@@ -189,9 +190,9 @@ namespace ICSharpCode.ILSpy.ViewModels
 			if (manager.AssemblyLists.Count > 0)
 			{
 				SelectedAssemblyList = manager.AssemblyLists[Math.Max(0, index - 1)];
-				if (MainWindow.Instance.SessionSettings.ActiveAssemblyList == assemblyList)
+				if (SettingsService.Instance.SessionSettings.ActiveAssemblyList == assemblyList)
 				{
-					MainWindow.Instance.SessionSettings.ActiveAssemblyList = SelectedAssemblyList;
+					SettingsService.Instance.SessionSettings.ActiveAssemblyList = SelectedAssemblyList;
 				}
 			}
 		}
@@ -232,9 +233,9 @@ namespace ICSharpCode.ILSpy.ViewModels
 				string assemblyList = SelectedAssemblyList;
 				SelectedAssemblyList = dlg.ListName;
 				manager.RenameList(assemblyList, dlg.ListName);
-				if (MainWindow.Instance.SessionSettings.ActiveAssemblyList == assemblyList)
+				if (SettingsService.Instance.SessionSettings.ActiveAssemblyList == assemblyList)
 				{
-					MainWindow.Instance.SessionSettings.ActiveAssemblyList = manager.AssemblyLists[manager.AssemblyLists.Count - 1];
+					SettingsService.Instance.SessionSettings.ActiveAssemblyList = manager.AssemblyLists[manager.AssemblyLists.Count - 1];
 				}
 			}
 		}
@@ -272,7 +273,7 @@ namespace ICSharpCode.ILSpy.ViewModels
 
 		private void ExecuteSelectAssemblyList()
 		{
-			MainWindow.Instance.SessionSettings.ActiveAssemblyList = SelectedAssemblyList;
+			SettingsService.Instance.SessionSettings.ActiveAssemblyList = SelectedAssemblyList;
 			this.parent.Close();
 		}
 	}

ILSpy/ViewModels/TabPageModel.cs

@@ -17,11 +17,10 @@
 // DEALINGS IN THE SOFTWARE.
 
 using System;
-using System.Collections.Generic;
-using System.Linq;
 using System.Threading.Tasks;
 
 using ICSharpCode.ILSpy.TextView;
+using ICSharpCode.ILSpy.Util;
 using ICSharpCode.ILSpyX;
 
 namespace ICSharpCode.ILSpy.ViewModels
@@ -33,29 +32,6 @@ namespace ICSharpCode.ILSpy.ViewModels
 			this.Title = Properties.Resources.NewTab;
 		}
 
-		private FilterSettings filterSettings;
-
-		public FilterSettings FilterSettings {
-			get => filterSettings;
-			set {
-				if (filterSettings != value)
-				{
-					filterSettings = value;
-					RaisePropertyChanged(nameof(FilterSettings));
-				}
-			}
-		}
-
-		public Language Language {
-			get => filterSettings.Language;
-			set => filterSettings.Language = value;
-		}
-
-		public LanguageVersion LanguageVersion {
-			get => filterSettings.LanguageVersion;
-			set => filterSettings.LanguageVersion = value;
-		}
-
 		private bool supportsLanguageSwitching = true;
 
 		public bool SupportsLanguageSwitching {

ILSpy/Views/DebugSteps.xaml.cs

@@ -29,16 +29,13 @@ namespace ICSharpCode.ILSpy
 #if DEBUG
 		ILAstLanguage language;
 #endif
-		FilterSettings filterSettings;
-
 		public DebugSteps()
 		{
 			InitializeComponent();
 
 #if DEBUG
-			MessageBus<DockWorkspaceActiveTabPageChangedEventArgs>.Subscribers += DockWorkspace_ActiveTabPageChanged;
-			filterSettings = DockWorkspace.Instance.ActiveTabPage.FilterSettings;
-			filterSettings.PropertyChanged += FilterSettings_PropertyChanged;
+			MessageBus<LanguageSettingsChangedEventArgs>.Subscribers += (sender, e) => LanguageSettings_PropertyChanged(sender, e);
+
 			MainWindow.Instance.SelectionChanged += SelectionChanged;
 			writingOptions.PropertyChanged += WritingOptions_PropertyChanged;
 
@@ -51,13 +48,6 @@ namespace ICSharpCode.ILSpy
 #endif
 		}
 
-		private void DockWorkspace_ActiveTabPageChanged(object sender, EventArgs e)
-		{
-			filterSettings.PropertyChanged -= FilterSettings_PropertyChanged;
-			filterSettings = DockWorkspace.Instance.ActiveTabPage.FilterSettings;
-			filterSettings.PropertyChanged += FilterSettings_PropertyChanged;
-		}
-
 		private void WritingOptions_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
 		{
 			DecompileAsync(lastSelectedStep);
@@ -71,7 +61,7 @@ namespace ICSharpCode.ILSpy
 			});
 		}
 
-		private void FilterSettings_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
+		private void LanguageSettings_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
 		{
 #if DEBUG
 			if (e.PropertyName == "Language")