diff --git a/Directory.Packages.props b/Directory.Packages.props
index f2fd119b5d..bcedfd1c10 100644
--- a/Directory.Packages.props
+++ b/Directory.Packages.props
@@ -45,12 +45,12 @@
     <PackageVersion Include="System.Reflection.Metadata" Version="8.0.0" />
     <PackageVersion Include="System.Resources.Extensions" Version="8.0.0" />
     <PackageVersion Include="System.Runtime.CompilerServices.Unsafe" Version="6.0.0" />
-    <PackageVersion Include="TomsToolbox.Wpf.Composition" Version="2.18.1" />
-    <PackageVersion Include="TomsToolbox.Wpf.Composition.Mef" Version="2.18.1" />
-    <PackageVersion Include="TomsToolbox.Wpf.Styles" Version="2.18.1" />
+    <PackageVersion Include="TomsToolbox.Wpf.Composition" Version="2.20.0" />
+    <PackageVersion Include="TomsToolbox.Wpf.Composition.Mef" Version="2.20.0" />
+    <PackageVersion Include="TomsToolbox.Wpf.Styles" Version="2.20.0" />
     <PackageVersion Include="coverlet.collector" Version="6.0.2" />
   </ItemGroup>
   <ItemGroup>
-    <GlobalPackageReference Include="TomsToolbox.Composition.Analyzer" Version="2.18.1" />
+    <GlobalPackageReference Include="TomsToolbox.Composition.Analyzer" Version="2.20.0" />
   </ItemGroup>
 </Project>
\ No newline at end of file
diff --git a/ICSharpCode.ILSpyX/AssemblyListManager.cs b/ICSharpCode.ILSpyX/AssemblyListManager.cs
index 35e1021ce9..772062c9e2 100644
--- a/ICSharpCode.ILSpyX/AssemblyListManager.cs
+++ b/ICSharpCode.ILSpyX/AssemblyListManager.cs
@@ -113,14 +113,16 @@ public bool RenameList(string selectedAssemblyList, string newListName)
 		public void SaveList(AssemblyList list)
 		{
 			this.settingsProvider.Update(
-				delegate (XElement root) {
+				root => {
 					XElement? doc = root.Element("AssemblyLists");
 					if (doc == null)
 					{
 						doc = new XElement("AssemblyLists");
 						root.Add(doc);
 					}
-					XElement? listElement = doc.Elements("List").FirstOrDefault(e => (string?)e.Attribute("name") == list.ListName);
+
+					XElement? listElement = doc.Elements("List")
+						.FirstOrDefault(e => (string?)e.Attribute("name") == list.ListName);
 					if (listElement != null)
 						listElement.ReplaceWith(list.SaveAsXml());
 					else
@@ -163,13 +165,9 @@ public void ClearAll()
 		{
 			AssemblyLists.Clear();
 			this.settingsProvider.Update(
-				delegate (XElement root) {
+				root => {
 					XElement? doc = root.Element("AssemblyLists");
-					if (doc == null)
-					{
-						return;
-					}
-					doc.Remove();
+					doc?.Remove();
 				});
 		}
 
diff --git a/ILSpy/Analyzers/AnalyzerTreeView.xaml b/ILSpy/Analyzers/AnalyzerTreeView.xaml
index 28bba030c8..d23119f127 100644
--- a/ILSpy/Analyzers/AnalyzerTreeView.xaml
+++ b/ILSpy/Analyzers/AnalyzerTreeView.xaml
@@ -12,8 +12,7 @@
 	ShowRoot="False"
 	BorderThickness="0"
 	Root="{Binding Root}"
-	toms:MultiSelectorExtensions.SelectionBinding="{Binding SelectedItems}"
-	SelectedItem="{Binding SelectedItem, Mode=TwoWay}"
+	toms:MultiSelectorExtensions.SelectionBinding="{Binding SelectedItems, Mode=TwoWay}"
 	SelectionChanged="AnalyzerTreeView_OnSelectionChanged">
 
 	<UIElement.InputBindings>
diff --git a/ILSpy/Analyzers/AnalyzerTreeViewModel.cs b/ILSpy/Analyzers/AnalyzerTreeViewModel.cs
index 7a746c0889..5c666d38f4 100644
--- a/ILSpy/Analyzers/AnalyzerTreeViewModel.cs
+++ b/ILSpy/Analyzers/AnalyzerTreeViewModel.cs
@@ -17,8 +17,6 @@
 // DEALINGS IN THE SOFTWARE.
 
 using System;
-using System.Collections.Generic;
-using System.Collections.ObjectModel;
 using System.ComponentModel.Composition;
 using System.Linq;
 using System.Windows;
@@ -38,8 +36,6 @@ namespace ICSharpCode.ILSpy.Analyzers
 	[Export]
 	public class AnalyzerTreeViewModel : ToolPaneModel
 	{
-		private AnalyzerTreeNode selectedItem;
-
 		public const string PaneContentId = "analyzerPane";
 
 		public AnalyzerTreeViewModel()
@@ -52,14 +48,20 @@ public AnalyzerTreeViewModel()
 
 		public AnalyzerRootNode Root { get; } = new();
 
-		public AnalyzerTreeNode SelectedItem {
-			get => selectedItem;
-			set => SetProperty(ref selectedItem, value);
-		}
-
 		public ICommand AnalyzeCommand => new DelegateCommand(AnalyzeSelected);
 
-		public ObservableCollection<AnalyzerTreeNode> SelectedItems { get; } = [];
+		private AnalyzerTreeNode[] selectedItems = [];
+
+		public AnalyzerTreeNode[] SelectedItems {
+			get => selectedItems ?? [];
+			set {
+				if (SelectedItems.SequenceEqual(value))
+					return;
+
+				selectedItems = value;
+				OnPropertyChanged();
+			}
+		}
 
 		private void AnalyzeSelected()
 		{
@@ -87,7 +89,7 @@ void AddOrSelect(AnalyzerTreeNode node)
 			}
 
 			target.IsExpanded = true;
-			this.SelectedItem = target;
+			this.SelectedItems = [target];
 		}
 
 		public void Analyze(IEntity entity)
diff --git a/ILSpy/App.xaml.cs b/ILSpy/App.xaml.cs
index d00eb42045..0665244f3f 100644
--- a/ILSpy/App.xaml.cs
+++ b/ILSpy/App.xaml.cs
@@ -216,9 +216,6 @@ protected override void OnStartup(StartupEventArgs e)
 			}
 
 			MainWindow = new MainWindow();
-			MainWindow.Loaded += (sender, args) => {
-				ExportProvider.GetExportedValue<AssemblyTreeModel>().Initialize();
-			};
 			MainWindow.Show();
 		}
 
diff --git a/ILSpy/AssemblyTree/AssemblyListPane.xaml b/ILSpy/AssemblyTree/AssemblyListPane.xaml
index 7222fdabff..e413985d7c 100644
--- a/ILSpy/AssemblyTree/AssemblyListPane.xaml
+++ b/ILSpy/AssemblyTree/AssemblyListPane.xaml
@@ -7,6 +7,7 @@
 						xmlns:treeNodes="clr-namespace:ICSharpCode.ILSpy.TreeNodes"
 						xmlns:assemblyTree="clr-namespace:ICSharpCode.ILSpy.AssemblyTree"
 						xmlns:toms="urn:TomsToolbox"
+						xmlns:viewModels="clr-namespace:ICSharpCode.ILSpy.ViewModels"
 						mc:Ignorable="d" d:DesignHeight="450" d:DesignWidth="800"
 						d:DataContext="{d:DesignInstance assemblyTree:AssemblyTreeModel}"
 						AutomationProperties.Name="Assemblies and Classes"
@@ -15,8 +16,8 @@
 						AllowDrop="True"
 						BorderThickness="0" Visibility="Visible"
 						Root="{Binding Root}"
-						SelectedItem="{Binding SelectedItem, Mode=TwoWay}"
-						toms:MultiSelectorExtensions.SelectionBinding="{Binding SelectedItems}">
+						toms:MultiSelectorExtensions.SelectionBinding="{Binding SelectedItems, Mode=TwoWay}"
+						viewModels:Pane.IsActive="{Binding IsActive}">
 	<treeView:SharpTreeView.ItemContainerStyle>
 		<Style TargetType="treeView:SharpTreeViewItem">
 			<Setter Property="Template">
diff --git a/ILSpy/AssemblyTree/AssemblyListPane.xaml.cs b/ILSpy/AssemblyTree/AssemblyListPane.xaml.cs
index 1f31ffc755..93e78a75da 100644
--- a/ILSpy/AssemblyTree/AssemblyListPane.xaml.cs
+++ b/ILSpy/AssemblyTree/AssemblyListPane.xaml.cs
@@ -20,6 +20,9 @@
 using System.Windows;
 using System.Windows.Threading;
 
+using ICSharpCode.ILSpy.ViewModels;
+using ICSharpCode.ILSpyX.TreeView;
+
 using TomsToolbox.Wpf.Composition.Mef;
 
 namespace ICSharpCode.ILSpy.AssemblyTree
@@ -59,6 +62,20 @@ protected override void OnPropertyChanged(DependencyPropertyChangedEventArgs e)
 					});
 				}
 			}
+			else if (e.Property == Pane.IsActiveProperty)
+			{
+				if (!true.Equals(e.NewValue))
+					return;
+
+				if (SelectedItem is SharpTreeNode selectedItem)
+				{
+					FocusNode(selectedItem);
+				}
+				else
+				{
+					Focus();
+				}
+			}
 		}
 	}
 }
diff --git a/ILSpy/AssemblyTree/AssemblyTreeModel.cs b/ILSpy/AssemblyTree/AssemblyTreeModel.cs
index de8237b081..63ce158f6f 100644
--- a/ILSpy/AssemblyTree/AssemblyTreeModel.cs
+++ b/ILSpy/AssemblyTree/AssemblyTreeModel.cs
@@ -18,7 +18,6 @@
 
 using System.Collections.Generic;
 using System;
-using System.Collections.ObjectModel;
 using System.ComponentModel.Composition;
 using System.IO;
 using System.Threading.Tasks;
@@ -82,10 +81,9 @@ public AssemblyTreeModel()
 			MessageBus<NavigateToReferenceEventArgs>.Subscribers += JumpToReference;
 			MessageBus<SettingsChangedEventArgs>.Subscribers += (sender, e) => Settings_PropertyChanged(sender, e);
 
-			var selectionChangeThrottle = new DispatcherThrottle(DispatcherPriority.Input, TreeView_SelectionChanged);
-			SelectedItems.CollectionChanged += (_, _) => selectionChangeThrottle.Tick();
-
 			refreshThrottle = new DispatcherThrottle(DispatcherPriority.Background, RefreshInternal);
+
+			AssemblyList = SettingsService.Instance.CreateEmptyAssemblyList();
 		}
 
 		private void Settings_PropertyChanged(object? sender, PropertyChangedEventArgs e)
@@ -121,7 +119,7 @@ private void Settings_PropertyChanged(object? sender, PropertyChangedEventArgs e
 			}
 		}
 
-		public AssemblyList? AssemblyList { get; private set; }
+		public AssemblyList AssemblyList { get; private set; }
 
 		private SharpTreeNode? root;
 		public SharpTreeNode? Root {
@@ -129,13 +127,23 @@ public SharpTreeNode? Root {
 			set => SetProperty(ref root, value);
 		}
 
-		private SharpTreeNode? selectedItem;
 		public SharpTreeNode? SelectedItem {
-			get => selectedItem;
-			set => SetProperty(ref selectedItem, value);
+			get => SelectedItems.FirstOrDefault();
+			set => SelectedItems = value is null ? [] : [value];
 		}
 
-		public ObservableCollection<SharpTreeNode> SelectedItems { get; } = [];
+		private SharpTreeNode[] selectedItems = [];
+		public SharpTreeNode[] SelectedItems {
+			get => selectedItems;
+			set {
+				if (selectedItems.SequenceEqual(value))
+					return;
+
+				selectedItems = value;
+				OnPropertyChanged();
+				TreeView_SelectionChanged();
+			}
+		}
 
 		public string[]? SelectedPath => GetPathForNode(SelectedItem);
 
@@ -205,7 +213,7 @@ private async void NavigateOnLaunch(string? navigateTo, string[]? activeTreeView
 						{
 							// FindNamespaceNode() blocks the UI if the assembly is not yet loaded,
 							// so use an async wait instead.
-							await asm.GetMetadataFileAsync().Catch<Exception>(ex => { });
+							await asm.GetMetadataFileAsync().Catch<Exception>(_ => { });
 							NamespaceTreeNode nsNode = asmNode.FindNamespaceNode(namespaceName);
 							if (nsNode != null)
 							{
@@ -228,9 +236,11 @@ private async void NavigateOnLaunch(string? navigateTo, string[]? activeTreeView
 				else
 				{
 					IEntity? mr = await Task.Run(() => FindEntityInRelevantAssemblies(navigateTo, relevantAssemblies));
+
 					// Make sure we wait for assemblies being loaded...
 					// BeginInvoke in LoadedAssembly.LookupReferencedAssemblyInternal
 					await Dispatcher.InvokeAsync(delegate { }, DispatcherPriority.Normal);
+
 					if (mr is { ParentModule.MetadataFile: not null })
 					{
 						found = true;
@@ -260,7 +270,7 @@ private async void NavigateOnLaunch(string? navigateTo, string[]? activeTreeView
 			else if (spySettings != null)
 			{
 				SharpTreeNode? node = null;
-				if (activeTreeViewPath?.Length > 0 && AssemblyList != null)
+				if (activeTreeViewPath?.Length > 0)
 				{
 					foreach (var asm in AssemblyList.GetAssemblies())
 					{
@@ -268,7 +278,7 @@ private async void NavigateOnLaunch(string? navigateTo, string[]? activeTreeView
 						{
 							// FindNodeByPath() blocks the UI if the assembly is not yet loaded,
 							// so use an async wait instead.
-							await asm.GetMetadataFileAsync().Catch<Exception>(ex => { });
+							await asm.GetMetadataFileAsync().Catch<Exception>(_ => { });
 						}
 					}
 					node = FindNodeByPath(activeTreeViewPath, true);
@@ -401,7 +411,7 @@ private void ShowAssemblyList(string name)
 		{
 			AssemblyList list = SettingsService.Instance.AssemblyListManager.LoadList(name);
 			//Only load a new list when it is a different one
-			if (list.ListName != AssemblyList?.ListName)
+			if (list.ListName != AssemblyList.ListName)
 			{
 				ShowAssemblyList(list);
 				SelectNode(Root);
@@ -411,12 +421,9 @@ private void ShowAssemblyList(string name)
 		private void ShowAssemblyList(AssemblyList assemblyList)
 		{
 			history.Clear();
-			if (this.AssemblyList != null)
-			{
-				this.AssemblyList.CollectionChanged -= assemblyList_CollectionChanged;
-			}
 
-			this.AssemblyList = assemblyList;
+			AssemblyList.CollectionChanged -= assemblyList_CollectionChanged;
+			AssemblyList = assemblyList;
 
 			assemblyList.CollectionChanged += assemblyList_CollectionChanged;
 
@@ -512,6 +519,10 @@ public void SelectNode(SharpTreeNode? node, bool inNewTabPage = false)
 			{
 				activeView?.ScrollIntoView(node);
 				SelectedItem = node;
+
+				Dispatcher.BeginInvoke(DispatcherPriority.Background, () => {
+					activeView?.ScrollIntoView(node);
+				});
 			}
 		}
 
@@ -527,32 +538,12 @@ public void SelectNodes(IEnumerable<SharpTreeNode> nodes)
 				return;
 			}
 
-			if (SelectedItems.SequenceEqual(nodesList))
+			foreach (var node in nodesList)
 			{
-				return;
+				activeView?.ScrollIntoView(node);
 			}
 
-			if (this.isNavigatingHistory)
-			{
-				SelectedItems.Clear();
-				foreach (var node in nodesList)
-				{
-					activeView?.ScrollIntoView(node);
-					SelectedItems.Add(node);
-				}
-			}
-			else
-			{
-				// defer selection change, so it does not interfere with the focus of the tab page.
-				Dispatcher.BeginInvoke(() => {
-					SelectedItems.Clear();
-					foreach (var node in nodesList)
-					{
-						activeView?.ScrollIntoView(node);
-						SelectedItems.Add(node);
-					}
-				});
-			}
+			SelectedItems = nodesList.ToArray();
 		}
 
 		/// <summary>
@@ -649,8 +640,6 @@ private Task JumpToReferenceAsync(object? reference, bool inNewTabPage = false)
 					MainWindow.OpenLink(opCode.Link);
 					break;
 				case EntityReference unresolvedEntity:
-					if (AssemblyList is null)
-						break;
 					string protocol = unresolvedEntity.Protocol;
 					var file = unresolvedEntity.ResolveAssembly(AssemblyList);
 					if (file == null)
@@ -696,8 +685,6 @@ private void LoadAssemblies(IEnumerable<string> fileNames, List<LoadedAssembly>?
 				AssemblyTreeNode? lastNode = null;
 
 				var assemblyList = AssemblyList;
-				if (assemblyList is null)
-					return;
 
 				foreach (string file in fileNames)
 				{
@@ -714,7 +701,7 @@ private void LoadAssemblies(IEnumerable<string> fileNames, List<LoadedAssembly>?
 						{
 							lastNode = node;
 							activeView?.ScrollIntoView(node);
-							SelectedItems.Add(node);
+							SelectedItems = [.. SelectedItems, node];
 						}
 					}
 				}
@@ -729,7 +716,7 @@ private void LoadAssemblies(IEnumerable<string> fileNames, List<LoadedAssembly>?
 
 		private void TreeView_SelectionChanged()
 		{
-			if (SelectedItems.Count > 0)
+			if (SelectedItems.Length > 0)
 			{
 				var activeTabPage = DockWorkspace.Instance.ActiveTabPage;
 
@@ -777,13 +764,13 @@ void ContextMenuClosed(object? sender, EventArgs e)
 			}
 		}
 
-		private void DecompileSelectedNodes(DecompilerTextViewState? newState = null)
+		public void DecompileSelectedNodes(DecompilerTextViewState? newState = null)
 		{
 			var activeTabPage = DockWorkspace.Instance.ActiveTabPage;
 
 			activeTabPage.SupportsLanguageSwitching = true;
 
-			if (SelectedItems.Count == 1)
+			if (SelectedItems.Length == 1)
 			{
 				if (SelectedItem is ILSpyTreeNode node && node.View(activeTabPage))
 					return;
@@ -818,23 +805,29 @@ public IEnumerable<ILSpyTreeNode> SelectedNodes {
 
 		public void NavigateHistory(bool forward)
 		{
-			isNavigatingHistory = true;
-			this.Dispatcher.BeginInvoke(DispatcherPriority.Background, () => isNavigatingHistory = false);
+			try
+			{
+				isNavigatingHistory = true;
 
-			TabPageModel tabPage = DockWorkspace.Instance.ActiveTabPage;
-			var state = tabPage.GetState();
-			if (state != null)
-				history.UpdateCurrent(new NavigationState(tabPage, state));
-			var newState = forward ? history.GoForward() : history.GoBack();
+				TabPageModel tabPage = DockWorkspace.Instance.ActiveTabPage;
+				var state = tabPage.GetState();
+				if (state != null)
+					history.UpdateCurrent(new NavigationState(tabPage, state));
+				var newState = forward ? history.GoForward() : history.GoBack();
 
-			TabPageModel activeTabPage = newState.TabPage;
+				TabPageModel activeTabPage = newState.TabPage;
 
-			if (!DockWorkspace.Instance.TabPages.Contains(activeTabPage))
-				DockWorkspace.Instance.AddTabPage(activeTabPage);
-			else
-				DockWorkspace.Instance.ActiveTabPage = activeTabPage;
+				if (!DockWorkspace.Instance.TabPages.Contains(activeTabPage))
+					DockWorkspace.Instance.AddTabPage(activeTabPage);
+				else
+					DockWorkspace.Instance.ActiveTabPage = activeTabPage;
 
-			SelectNodes(newState.TreeNodes);
+				SelectNodes(newState.TreeNodes);
+			}
+			finally
+			{
+				isNavigatingHistory = false;
+			}
 		}
 
 		public bool CanNavigateBack => history.CanNavigateBack;
@@ -907,11 +900,7 @@ private void RefreshInternal()
 			{
 				var path = GetPathForNode(SelectedItem);
 
-				if (AssemblyList != null)
-				{
-					ShowAssemblyList(SettingsService.Instance.AssemblyListManager.LoadList(AssemblyList.ListName));
-				}
-
+				ShowAssemblyList(SettingsService.Instance.AssemblyListManager.LoadList(AssemblyList.ListName));
 				SelectNode(FindNodeByPath(path, true), inNewTabPage: false);
 
 				RefreshDecompiledView();
@@ -920,7 +909,7 @@ private void RefreshInternal()
 
 		private void UnselectAll()
 		{
-			SelectedItems.Clear();
+			SelectedItems = [];
 		}
 
 		private IEnumerable<SharpTreeNode> GetTopLevelSelection()
@@ -940,7 +929,7 @@ public void SortAssemblyList()
 		{
 			using (activeView?.LockUpdates())
 			{
-				AssemblyList?.Sort(AssemblyComparer.Instance);
+				AssemblyList.Sort(AssemblyComparer.Instance);
 			}
 		}
 
diff --git a/ILSpy/Commands/DecompileInNewViewCommand.cs b/ILSpy/Commands/DecompileInNewViewCommand.cs
index fd83244ebd..40df5145a1 100644
--- a/ILSpy/Commands/DecompileInNewViewCommand.cs
+++ b/ILSpy/Commands/DecompileInNewViewCommand.cs
@@ -23,9 +23,11 @@
 using System.Windows.Threading;
 
 using ICSharpCode.Decompiler.TypeSystem;
+using ICSharpCode.ILSpy.AssemblyTree;
 using ICSharpCode.ILSpy.Docking;
 using ICSharpCode.ILSpy.Properties;
 using ICSharpCode.ILSpy.TreeNodes;
+using ICSharpCode.ILSpy.ViewModels;
 
 using TomsToolbox.Essentials;
 
@@ -35,6 +37,14 @@ namespace ICSharpCode.ILSpy.Commands
 	[PartCreationPolicy(CreationPolicy.Shared)]
 	internal sealed class DecompileInNewViewCommand : IContextMenuEntry
 	{
+		private readonly AssemblyTreeModel assemblyTreeModel;
+
+		[ImportingConstructor]
+		public DecompileInNewViewCommand(AssemblyTreeModel assemblyTreeModel)
+		{
+			this.assemblyTreeModel = assemblyTreeModel;
+		}
+
 		public bool IsVisible(TextViewContext context)
 		{
 			return context.SelectedTreeNodes != null || context.Reference?.Reference is IEntity;
@@ -47,14 +57,18 @@ public bool IsEnabled(TextViewContext context)
 
 		public void Execute(TextViewContext context)
 		{
+			var activePane = DockWorkspace.Instance.ActivePane;
+
 			DecompileNodes(GetNodes(context).ToArray());
+
+			DockWorkspace.Instance.ActivePane = activePane;
 		}
 
 		IEnumerable<ILSpyTreeNode> GetNodes(TextViewContext context)
 		{
 			if (context.SelectedTreeNodes != null)
 			{
-				if (context.TreeView.DataContext != MainWindow.Instance.AssemblyTreeModel)
+				if (context.TreeView.DataContext != assemblyTreeModel)
 				{
 					return context.SelectedTreeNodes.OfType<IMemberTreeNode>().Select(FindTreeNode).ExceptNullItems();
 				}
@@ -65,7 +79,7 @@ IEnumerable<ILSpyTreeNode> GetNodes(TextViewContext context)
 			}
 			else if (context.Reference?.Reference is IEntity entity)
 			{
-				if (MainWindow.Instance.AssemblyTreeModel.FindTreeNode(entity) is { } node)
+				if (assemblyTreeModel.FindTreeNode(entity) is { } node)
 				{
 					return new[] { node };
 				}
@@ -76,18 +90,21 @@ ILSpyTreeNode FindTreeNode(IMemberTreeNode node)
 			{
 				if (node is ILSpyTreeNode ilspyNode)
 					return ilspyNode;
-				return MainWindow.Instance.AssemblyTreeModel.FindTreeNode(node.Member);
+				return assemblyTreeModel.FindTreeNode(node.Member);
 			}
 		}
 
-		static void DecompileNodes(ILSpyTreeNode[] nodes)
+		void DecompileNodes(ILSpyTreeNode[] nodes)
 		{
 			if (nodes.Length == 0)
 				return;
 
 			DockWorkspace.Instance.AddTabPage();
 
-			MainWindow.Instance.AssemblyTreeModel.SelectNodes(nodes);
+			if (assemblyTreeModel.SelectedItems.SequenceEqual(nodes))
+				assemblyTreeModel.DecompileSelectedNodes();
+			else
+				assemblyTreeModel.SelectNodes(nodes);
 		}
 	}
 }
diff --git a/ILSpy/Commands/RemoveAssembliesWithLoadErrors.cs b/ILSpy/Commands/RemoveAssembliesWithLoadErrors.cs
index 9cc357374a..b0bc068c88 100644
--- a/ILSpy/Commands/RemoveAssembliesWithLoadErrors.cs
+++ b/ILSpy/Commands/RemoveAssembliesWithLoadErrors.cs
@@ -19,6 +19,7 @@
 using System.ComponentModel.Composition;
 using System.Linq;
 
+using ICSharpCode.ILSpy.AssemblyTree;
 using ICSharpCode.ILSpy.Properties;
 
 namespace ICSharpCode.ILSpy
@@ -27,18 +28,26 @@ namespace ICSharpCode.ILSpy
 	[PartCreationPolicy(CreationPolicy.Shared)]
 	class RemoveAssembliesWithLoadErrors : SimpleCommand
 	{
+		private readonly AssemblyTreeModel assemblyTreeModel;
+
+		[ImportingConstructor]
+		public RemoveAssembliesWithLoadErrors(AssemblyTreeModel assemblyTreeModel)
+		{
+			this.assemblyTreeModel = assemblyTreeModel;
+		}
+
 		public override bool CanExecute(object parameter)
 		{
-			return MainWindow.Instance.AssemblyTreeModel.AssemblyList?.GetAssemblies().Any(l => l.HasLoadError) == true;
+			return assemblyTreeModel.AssemblyList.GetAssemblies().Any(l => l.HasLoadError);
 		}
 
 		public override void Execute(object parameter)
 		{
-			foreach (var asm in MainWindow.Instance.AssemblyTreeModel.AssemblyList.GetAssemblies())
+			foreach (var assembly in assemblyTreeModel.AssemblyList.GetAssemblies())
 			{
-				if (!asm.HasLoadError)
+				if (!assembly.HasLoadError)
 					continue;
-				var node = MainWindow.Instance.AssemblyTreeModel.FindAssemblyNode(asm);
+				var node = MainWindow.Instance.AssemblyTreeModel.FindAssemblyNode(assembly);
 				if (node != null && node.CanDelete())
 					node.Delete();
 			}
@@ -49,14 +58,22 @@ public override void Execute(object parameter)
 	[PartCreationPolicy(CreationPolicy.Shared)]
 	class ClearAssemblyList : SimpleCommand
 	{
+		private readonly AssemblyTreeModel assemblyTreeModel;
+
+		[ImportingConstructor]
+		public ClearAssemblyList(AssemblyTreeModel assemblyTreeModel)
+		{
+			this.assemblyTreeModel = assemblyTreeModel;
+		}
+
 		public override bool CanExecute(object parameter)
 		{
-			return MainWindow.Instance.AssemblyTreeModel.AssemblyList?.Count > 0;
+			return assemblyTreeModel.AssemblyList.Count > 0;
 		}
 
 		public override void Execute(object parameter)
 		{
-			MainWindow.Instance.AssemblyTreeModel.AssemblyList?.Clear();
+			assemblyTreeModel.AssemblyList.Clear();
 		}
 	}
 }
diff --git a/ILSpy/Commands/ShowPane.cs b/ILSpy/Commands/ShowPane.cs
index 372081e0ba..1c6694bd96 100644
--- a/ILSpy/Commands/ShowPane.cs
+++ b/ILSpy/Commands/ShowPane.cs
@@ -1,5 +1,4 @@
 using ICSharpCode.ILSpy.Docking;
-using ICSharpCode.ILSpy.Properties;
 using ICSharpCode.ILSpy.ViewModels;
 
 namespace ICSharpCode.ILSpy.Commands
@@ -30,7 +29,13 @@ public TabPageCommand(TabPageModel model)
 
 		public override void Execute(object parameter)
 		{
-			DockWorkspace.Instance.ActiveTabPage = model;
+			var workspace = DockWorkspace.Instance;
+
+			// ensure the tab control is focused before setting the active tab page, else the tab will not be focused
+			workspace.ActiveTabPage?.Focus();
+			// reset first, else clicking on the already active tab will not focus the tab and the menu checkmark will not be updated
+			workspace.ActiveTabPage = null;
+			workspace.ActiveTabPage = model;
 		}
 	}
 }
\ No newline at end of file
diff --git a/ILSpy/Controls/TreeView/SharpTreeView.cs b/ILSpy/Controls/TreeView/SharpTreeView.cs
index 80558388e4..4c99b4b458 100644
--- a/ILSpy/Controls/TreeView/SharpTreeView.cs
+++ b/ILSpy/Controls/TreeView/SharpTreeView.cs
@@ -416,7 +416,9 @@ public void ScrollIntoView(SharpTreeNode node)
 				throw new ArgumentNullException("node");
 			doNotScrollOnExpanding = true;
 			foreach (SharpTreeNode ancestor in node.Ancestors())
+			{
 				ancestor.IsExpanded = true;
+			}
 			doNotScrollOnExpanding = false;
 			base.ScrollIntoView(node);
 		}
diff --git a/ILSpy/Docking/CloseAllDocumentsCommand.cs b/ILSpy/Docking/CloseAllDocumentsCommand.cs
index 2c0ceb41be..14169498f4 100644
--- a/ILSpy/Docking/CloseAllDocumentsCommand.cs
+++ b/ILSpy/Docking/CloseAllDocumentsCommand.cs
@@ -1,9 +1,4 @@
-using System;
-using System.Collections.Generic;
-using System.ComponentModel.Composition;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+using System.ComponentModel.Composition;
 
 using ICSharpCode.ILSpy.Properties;
 
diff --git a/ILSpy/Docking/DockWorkspace.cs b/ILSpy/Docking/DockWorkspace.cs
index 9ca68cc266..b196f8e79d 100644
--- a/ILSpy/Docking/DockWorkspace.cs
+++ b/ILSpy/Docking/DockWorkspace.cs
@@ -17,6 +17,7 @@
 // DEALINGS IN THE SOFTWARE.
 
 using System;
+using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.Collections.Specialized;
 using System.Linq;
@@ -34,7 +35,6 @@
 using ICSharpCode.ILSpy.Search;
 using ICSharpCode.ILSpy.TextView;
 using ICSharpCode.ILSpy.ViewModels;
-using ICSharpCode.ILSpyX.Extensions;
 
 using TomsToolbox.Composition;
 using TomsToolbox.Essentials;
@@ -51,13 +51,19 @@ public class DockWorkspace : ObservableObject, ILayoutUpdateStrategy
 		public static readonly DockWorkspace Instance = new();
 
 		private readonly ObservableCollection<TabPageModel> tabPages = [];
-		private readonly ObservableCollection<ToolPaneModel> toolPanes = [];
+
+		private DockingManager dockingManager;
 
 		private DockWorkspace()
 		{
 			this.tabPages.CollectionChanged += TabPages_CollectionChanged;
 			TabPages = new(tabPages);
-			ToolPanes = new(toolPanes);
+
+			ToolPanes = exportProvider
+				.GetExportedValues<ToolPaneModel>("ToolPane")
+				.OrderBy(item => item.Title)
+				.ToArray()
+				.AsReadOnly();
 
 			// Make sure there is at least one tab open
 			AddTabPage();
@@ -83,11 +89,16 @@ private void CurrentAssemblyList_Changed(object sender, NotifyCollectionChangedE
 					.ExceptNullItems()
 					.Any(assemblyNode => !e.OldItems.Contains(assemblyNode.LoadedAssembly));
 
-				if (!found && tabPages.Count > 1)
+				if (!found)
 				{
 					tabPages.Remove(tab);
 				}
 			}
+
+			if (tabPages.Count == 0)
+			{
+				AddTabPage();
+			}
 		}
 
 		private void TabPages_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
@@ -117,11 +128,11 @@ public void AddTabPage(TabPageModel tabPage = null)
 
 		public ReadOnlyObservableCollection<TabPageModel> TabPages { get; }
 
-		public ReadOnlyObservableCollection<ToolPaneModel> ToolPanes { get; }
+		public ReadOnlyCollection<ToolPaneModel> ToolPanes { get; }
 
 		public bool ShowToolPane(string contentId)
 		{
-			var pane = toolPanes.FirstOrDefault(p => p.ContentId == contentId);
+			var pane = ToolPanes.FirstOrDefault(p => p.ContentId == contentId);
 			if (pane != null)
 			{
 				pane.Show();
@@ -132,10 +143,15 @@ public bool ShowToolPane(string contentId)
 
 		public void Remove(PaneModel model)
 		{
-			if (model is TabPageModel document)
-				tabPages.Remove(document);
-			if (model is ToolPaneModel tool)
-				tool.IsVisible = false;
+			switch (model)
+			{
+				case TabPageModel document:
+					tabPages.Remove(document);
+					break;
+				case ToolPaneModel tool:
+					tool.IsVisible = false;
+					break;
+			}
 		}
 
 		private TabPageModel activeTabPage = null;
@@ -164,12 +180,17 @@ public TabPageModel ActiveTabPage {
 			}
 		}
 
+		public PaneModel ActivePane {
+			get => dockingManager?.ActiveContent as PaneModel;
+			set {
+				if (dockingManager is not null)
+					dockingManager.ActiveContent = value;
+			}
+		}
+
 		public void InitializeLayout(DockingManager manager)
 		{
-			var panes = exportProvider.GetExportedValues<ToolPaneModel>("ToolPane").OrderBy(item => item.Title);
-
-			this.toolPanes.AddRange(panes);
-
+			this.dockingManager = manager;
 			manager.LayoutUpdateStrategy = this;
 			XmlLayoutSerializer serializer = new XmlLayoutSerializer(manager);
 			serializer.LayoutSerializationCallback += LayoutSerializationCallback;
@@ -188,13 +209,13 @@ void LayoutSerializationCallback(object sender, LayoutSerializationCallbackEvent
 			switch (e.Model)
 			{
 				case LayoutAnchorable la:
-					e.Content = this.toolPanes.FirstOrDefault(p => p.ContentId == la.ContentId);
+					e.Content = this.ToolPanes.FirstOrDefault(p => p.ContentId == la.ContentId);
 					e.Cancel = e.Content == null;
 					la.CanDockAsTabbedDocument = false;
-					if (!e.Cancel)
+					if (e.Content is ToolPaneModel toolPaneModel)
 					{
-						e.Cancel = ((ToolPaneModel)e.Content).IsVisible;
-						((ToolPaneModel)e.Content).IsVisible = true;
+						e.Cancel = toolPaneModel.IsVisible;
+						toolPaneModel.IsVisible = true;
 					}
 					break;
 				default:
@@ -220,16 +241,14 @@ internal void ShowNodes(AvalonEditTextOutput output, TreeNodes.ILSpyTreeNode[] n
 
 		internal void CloseAllTabs()
 		{
-			foreach (var doc in tabPages.ToArray())
-			{
-				if (doc.IsCloseable)
-					tabPages.Remove(doc);
-			}
+			var activePage = ActiveTabPage;
+
+			tabPages.RemoveWhere(page => page != activePage);
 		}
 
 		internal void ResetLayout()
 		{
-			foreach (var pane in toolPanes)
+			foreach (var pane in ToolPanes)
 			{
 				pane.IsVisible = false;
 			}
diff --git a/ILSpy/MainWindow.xaml.cs b/ILSpy/MainWindow.xaml.cs
index c5232ef831..981da03e88 100644
--- a/ILSpy/MainWindow.xaml.cs
+++ b/ILSpy/MainWindow.xaml.cs
@@ -25,6 +25,7 @@
 using System.Windows;
 using System.Windows.Input;
 using System.Windows.Media;
+using System.Windows.Threading;
 
 using AvalonDock.Layout.Serialization;
 
@@ -70,11 +71,17 @@ public MainWindow()
 
 			InitializeComponent();
 
-			mainWindowViewModel.Workspace.InitializeLayout(dockManager);
+			InitFileLoaders();
 
-			MenuService.Instance.Init(mainMenu, toolBar, InputBindings);
+			Dispatcher.BeginInvoke(DispatcherPriority.Background, () => {
+				mainWindowViewModel.Workspace.InitializeLayout(dockManager);
+				MenuService.Instance.Init(mainMenu, toolBar, InputBindings);
 
-			InitFileLoaders();
+				Dispatcher.BeginInvoke(DispatcherPriority.Background, () => {
+					AssemblyTreeModel.Initialize();
+					AssemblyTreeModel.Show();
+				});
+			});
 		}
 
 		void SetWindowBounds(Rect bounds)
diff --git a/ILSpy/Util/MenuService.cs b/ILSpy/Util/MenuService.cs
index d364ad4389..6b1d2e29dc 100644
--- a/ILSpy/Util/MenuService.cs
+++ b/ILSpy/Util/MenuService.cs
@@ -142,7 +142,7 @@ void InitWindowMenu(Menu mainMenu, InputBindingCollection inputBindings)
 
 			windowMenuItem.Items.Clear();
 
-			var toolItems = dockWorkspace.ToolPanes.ObservableSelect(toolPane => CreateMenuItem(toolPane, inputBindings));
+			var toolItems = dockWorkspace.ToolPanes.Select(toolPane => CreateMenuItem(toolPane, inputBindings)).ToArray();
 			var tabItems = dockWorkspace.TabPages.ObservableSelect(tabPage => CreateMenuItem(tabPage, dockWorkspace));
 
 			var allItems = new ObservableCompositeCollection<Control>(defaultItems, [new Separator()], toolItems, [new Separator()], tabItems);
@@ -207,7 +207,8 @@ static Control CreateMenuItem(TabPageModel pane, DockWorkspace dock)
 			menuItem.SetBinding(MenuItem.IsCheckedProperty, new Binding(nameof(dock.ActiveTabPage)) {
 				Source = dock,
 				ConverterParameter = pane,
-				Converter = BinaryOperationConverter.Equality
+				Converter = BinaryOperationConverter.Equality,
+				Mode = BindingMode.OneWay
 			});
 
 			return menuItem;
diff --git a/ILSpy/Util/SettingsService.cs b/ILSpy/Util/SettingsService.cs
index def1ccf211..bd2923e2e5 100644
--- a/ILSpy/Util/SettingsService.cs
+++ b/ILSpy/Util/SettingsService.cs
@@ -152,6 +152,11 @@ public AssemblyList LoadInitialAssemblyList()
 			}
 		}
 
+		public AssemblyList CreateEmptyAssemblyList()
+		{
+			return AssemblyListManager.CreateList(string.Empty);
+		}
+
 		private bool reloading;
 
 		public void Reload()
diff --git a/ILSpy/ViewModels/TabPageModel.cs b/ILSpy/ViewModels/TabPageModel.cs
index abcaa46660..691d7d28c2 100644
--- a/ILSpy/ViewModels/TabPageModel.cs
+++ b/ILSpy/ViewModels/TabPageModel.cs
@@ -17,10 +17,14 @@
 // DEALINGS IN THE SOFTWARE.
 
 using System;
+using System.Linq;
 using System.Threading.Tasks;
+using System.Windows;
 
 using ICSharpCode.ILSpy.TextView;
 
+using TomsToolbox.Wpf;
+
 namespace ICSharpCode.ILSpy.ViewModels
 {
 	public class TabPageModel : PaneModel
@@ -96,6 +100,19 @@ public static void ShowTextView(this TabPageModel tabPage, Action<DecompilerText
 			tabPage.Title = Properties.Resources.Decompiling;
 			action(textView);
 		}
+
+		public static void Focus(this TabPageModel tabPage)
+		{
+			if (tabPage.Content is not FrameworkElement content)
+				return;
+
+			var focusable = content
+				.VisualDescendantsAndSelf()
+				.OfType<FrameworkElement>()
+				.FirstOrDefault(item => item.Focusable);
+
+			focusable?.Focus();
+		}
 	}
 
 	public interface IHaveState