Omit the need for a special PaneCollection

ILSpy/AssemblyTree/AssemblyListPaneModel.cs

@@ -481,7 +481,7 @@ namespace ICSharpCode.ILSpy.AssemblyTree
 
 			if (inNewTabPage)
 			{
-				DockWorkspace.Instance.TabPages.Add();
+				DockWorkspace.Instance.AddTabPage();
 				SelectedItem = null;
 			}
 
@@ -505,7 +505,7 @@ namespace ICSharpCode.ILSpy.AssemblyTree
 
 				if (inNewTabPage)
 				{
-					DockWorkspace.Instance.TabPages.Add();
+					DockWorkspace.Instance.AddTabPage();
 				}
 
 				// Ensure nodes exist

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;
@@ -49,9 +50,15 @@ namespace ICSharpCode.ILSpy.Docking
 
 		public static readonly DockWorkspace Instance = new();
 
+		private readonly ObservableCollection<TabPageModel> tabPages = [];
+		private readonly ObservableCollection<ToolPaneModel> toolPanes = [];
+
 		private DockWorkspace()
 		{
-			this.TabPages.CollectionChanged += Documents_CollectionChanged;
+			this.tabPages.CollectionChanged += TabPages_CollectionChanged;
+			TabPages = new(tabPages);
+			ToolPanes = new(toolPanes);
+
 			MessageBus<CurrentAssemblyListChangedEventArgs>.Subscribers += (sender, e) => CurrentAssemblyList_Changed(sender, e);
 		}
 
@@ -61,7 +68,7 @@ namespace ICSharpCode.ILSpy.Docking
 			{
 				return;
 			}
-			foreach (var tab in TabPages.ToArray())
+			foreach (var tab in tabPages.ToArray())
 			{
 				var state = tab.GetState();
 				if (state == null || state.DecompiledNodes == null)
@@ -78,35 +85,45 @@ namespace ICSharpCode.ILSpy.Docking
 						break;
 					}
 				}
-				if (!found && TabPages.Count > 1)
+				if (!found && tabPages.Count > 1)
 				{
-					TabPages.Remove(tab);
+					tabPages.Remove(tab);
 				}
 			}
 		}
 
-		private void Documents_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
+		private void TabPages_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
 		{
-			var collection = (PaneCollection<TabPageModel>)sender;
 			if (e.Action == NotifyCollectionChangedAction.Add)
 			{
-				ActiveTabPage = e.NewItems?[0] as TabPageModel;
+				if (e.NewItems?[0] is TabPageModel model)
+				{
+					ActiveTabPage = model;
+					model.IsActive = true;
+					model.IsVisible = true;
+				}
 			}
 
-			bool canClose = collection.Count > 1;
+			bool canClose = tabPages.Count > 1;
-			foreach (var item in collection)
+
+			foreach (var item in tabPages)
 			{
 				item.IsCloseable = canClose;
 			}
 		}
 
-		public PaneCollection<TabPageModel> TabPages { get; } = new PaneCollection<TabPageModel>();
+		public void AddTabPage(TabPageModel tabPage = null)
+		{
+			tabPages.Add(tabPage ?? new TabPageModel());
+		}
 
-		public ObservableCollection<ToolPaneModel> ToolPanes { get; } = new ObservableCollection<ToolPaneModel>();
+		public ReadOnlyObservableCollection<TabPageModel> TabPages { get; }
+
+		public ReadOnlyObservableCollection<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();
@@ -118,7 +135,7 @@ namespace ICSharpCode.ILSpy.Docking
 		public void Remove(PaneModel model)
 		{
 			if (model is TabPageModel document)
-				TabPages.Remove(document);
+				tabPages.Remove(document);
 			if (model is ToolPaneModel tool)
 				tool.IsVisible = false;
 		}
@@ -153,7 +170,8 @@ namespace ICSharpCode.ILSpy.Docking
 		public void InitializeLayout(DockingManager manager)
 		{
 			var toolPanes = exportProvider.GetExportedValues<ToolPaneModel>("ToolPane").OrderBy(item => item.Title);
-			ToolPanes.AddRange(toolPanes);
+
+			this.toolPanes.AddRange(toolPanes);
 
 			manager.LayoutUpdateStrategy = this;
 			XmlLayoutSerializer serializer = new XmlLayoutSerializer(manager);
@@ -173,7 +191,7 @@ namespace ICSharpCode.ILSpy.Docking
 			switch (e.Model)
 			{
 				case LayoutAnchorable la:
-					e.Content = 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)
@@ -205,16 +223,16 @@ namespace ICSharpCode.ILSpy.Docking
 
 		internal void CloseAllTabs()
 		{
-			foreach (var doc in TabPages.ToArray())
+			foreach (var doc in tabPages.ToArray())
 			{
 				if (doc.IsCloseable)
-					TabPages.Remove(doc);
+					tabPages.Remove(doc);
 			}
 		}
 
 		internal void ResetLayout()
 		{
-			foreach (var pane in ToolPanes)
+			foreach (var pane in toolPanes)
 			{
 				pane.IsVisible = false;
 			}

ILSpy/Docking/PaneCollection.cs

@@ -1,66 +0,0 @@
-// Copyright (c) 2019 AlphaSierraPapa for the SharpDevelop Team
-// 
-// Permission is hereby granted, free of charge, to any person obtaining a copy of this
-// software and associated documentation files (the "Software"), to deal in the Software
-// without restriction, including without limitation the rights to use, copy, modify, merge,
-// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
-// to whom the Software is furnished to do so, subject to the following conditions:
-// 
-// The above copyright notice and this permission notice shall be included in all copies or
-// substantial portions of the Software.
-// 
-// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
-// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
-// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
-// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
-// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
-// DEALINGS IN THE SOFTWARE.
-
-using System;
-using System.Collections;
-using System.Collections.Generic;
-using System.Collections.ObjectModel;
-using System.Collections.Specialized;
-
-using ICSharpCode.ILSpy.ViewModels;
-
-namespace ICSharpCode.ILSpy.Docking
-{
-	public class PaneCollection<T> : INotifyCollectionChanged, IList<T>
-		where T : PaneModel, new()
-	{
-		private readonly ObservableCollection<T> observableCollection = [];
-
-		public event NotifyCollectionChangedEventHandler CollectionChanged;
-
-		public PaneCollection()
-		{
-			observableCollection.CollectionChanged += (sender, e) => CollectionChanged?.Invoke(this, e);
-		}
-
-		public void Add(T item = null)
-		{
-			item ??= new T();
-
-			observableCollection.Add(item);
-
-			item.IsVisible = true;
-			item.IsActive = true;
-		}
-		public int Count => observableCollection.Count;
-		public bool IsReadOnly => false;
-		public void Clear() => observableCollection.Clear();
-		public bool Contains(T item) => observableCollection.Contains(item);
-		public void CopyTo(T[] array, int arrayIndex) => observableCollection.CopyTo(array, arrayIndex);
-		public bool Remove(T item) => observableCollection.Remove(item);
-		public IEnumerator<T> GetEnumerator() => observableCollection.GetEnumerator();
-		IEnumerator IEnumerable.GetEnumerator() => observableCollection.GetEnumerator();
-		int IList<T>.IndexOf(T item) => observableCollection.IndexOf(item);
-		void IList<T>.Insert(int index, T item) => throw new NotImplementedException("Only Add is supported");
-		void IList<T>.RemoveAt(int index) => observableCollection.RemoveAt(index);
-		T IList<T>.this[int index] {
-			get => observableCollection[index];
-			set => observableCollection[index] = value;
-		}
-	}
-}

ILSpy/MainWindow.xaml.cs

@@ -191,7 +191,7 @@ namespace ICSharpCode.ILSpy
 
 		void MainWindow_Loaded(object sender, RoutedEventArgs e)
 		{
-			DockWorkspace.Instance.TabPages.Add();
+			DockWorkspace.Instance.AddTabPage();
 
 			AssemblyTreeModel.Initialize();
 		}
@@ -380,7 +380,7 @@ namespace ICSharpCode.ILSpy
 			{
 				if (inNewTabPage)
 				{
-					DockWorkspace.Instance.TabPages.Add();
+					DockWorkspace.Instance.AddTabPage();
 				}
 
 				if (e.Uri.Host == "aboutpage")