Assembly tree pane scaffolding

Adds the assembly tree pane (DataGrid-based, ProDataGrid hierarchical
rows), the SharpTreeNode-derived node type skeletons it consumes, the
empty MainToolBar placeholder, the ILSpySettings file-path provider
wiring in App.axaml.cs, and the AssemblyTreeModel.Initialize() hook in
the MainWindow code-behind.

Assisted-by: Claude:claude-opus-4-7:Claude Code

ILSpy.Tests/AssemblyTree/AssemblyTreeModelTests.cs

@@ -0,0 +1,49 @@
+// Copyright (c) 2026 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 Avalonia.Headless.NUnit;
+
+using AwesomeAssertions;
+
+using ILSpy.AppEnv;
+using ILSpy.AssemblyTree;
+
+using NUnit.Framework;
+
+namespace ICSharpCode.ILSpy.Tests.AssemblyTree;
+
+// AssemblyTreeModel is the MEF-shared root of the assembly tree. Initialize() loads
+// (or creates) the default assembly list from settings, optionally bootstraps it with
+// the three .NET runtime assemblies, and wires Root to an AssemblyListTreeNode. If
+// either AssemblyList or Root stays null, the entire pane below is blank — which is
+// hard to debug from a UI snapshot, so we catch it at the model layer here.
+[TestFixture]
+public class AssemblyTreeModelTests
+{
+	[AvaloniaTest]
+	public void Initialize_populates_AssemblyList_and_Root()
+	{
+		var model = AppComposition.Current.GetExport<AssemblyTreeModel>();
+		model.Should().NotBeNull("AssemblyTreeModel is [Export][Shared] in ILSpy.AssemblyTree.");
+
+		model.Initialize();
+
+		model.AssemblyList.Should().NotBeNull("Initialize loads or creates the default AssemblyList.");
+		model.Root.Should().NotBeNull("Initialize wires Root to an AssemblyListTreeNode of the loaded list.");
+	}
+}

ILSpy/App.axaml.cs

@@ -18,13 +18,16 @@
 
 using System;
 using System.Composition.Hosting;
+using System.Diagnostics;
+using System.IO;
 
 using Avalonia;
 using Avalonia.Controls.ApplicationLifetimes;
 using Avalonia.Markup.Xaml;
 
+using ICSharpCode.ILSpyX.Settings;
+
 using ILSpy.AppEnv;
-using ILSpy.ViewModels;
 using ILSpy.Views;
 
 namespace ILSpy
@@ -45,6 +48,23 @@ namespace ILSpy
 
 			CommandLineArguments = CommandLineArguments.Create(Environment.GetCommandLineArgs()[1..]);
 
+			ILSpySettings.SettingsFilePathProvider = () => {
+				if (App.CommandLineArguments.ConfigFile != null)
+					return App.CommandLineArguments.ConfigFile;
+
+				var assemblyLocation = typeof(MainWindow).Assembly.Location;
+				if (!String.IsNullOrWhiteSpace(assemblyLocation))
+				{
+					var assemblyDirectory = Path.GetDirectoryName(assemblyLocation);
+					Debug.Assert(assemblyDirectory != null);
+					string localPath = Path.Combine(assemblyDirectory, "ILSpy.xml");
+					if (File.Exists(localPath))
+						return localPath;
+				}
+
+				return Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "ICSharpCode", "ILSpy.xml");
+			};
+
 			try
 			{
 				Composition = AppComposition.Initialize();

ILSpy/AssemblyTree/AssemblyListPane.axaml

@@ -0,0 +1,28 @@
+<UserControl xmlns="https://github.com/avaloniaui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+             xmlns:tree="using:ILSpy.AssemblyTree"
+             mc:Ignorable="d" d:DesignWidth="300" d:DesignHeight="450"
+             x:Class="ILSpy.AssemblyTree.AssemblyListPane"
+             x:DataType="tree:AssemblyTreeModel">
+
+	<DataGrid Name="TreeGrid"
+	          HeadersVisibility="None"
+	          HierarchicalRowsEnabled="True"
+	          GridLinesVisibility="None"
+	          IsReadOnly="True"
+	          CanUserResizeColumns="False"
+	          SelectionMode="Single">
+		<DataGrid.Columns>
+			<DataGridTemplateColumn Header="Name" Width="*">
+				<DataGridTemplateColumn.CellTemplate>
+					<DataTemplate>
+						<TextBlock Text="{ReflectionBinding Item.Text}"
+						           VerticalAlignment="Center" Margin="4,0" />
+					</DataTemplate>
+				</DataGridTemplateColumn.CellTemplate>
+			</DataGridTemplateColumn>
+		</DataGrid.Columns>
+	</DataGrid>
+</UserControl>

ILSpy/AssemblyTree/AssemblyListPane.axaml.cs

@@ -0,0 +1,70 @@
+// Copyright (c) 2026 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.Collections;
+using System.ComponentModel;
+
+using Avalonia.Controls;
+using Avalonia.Controls.DataGridHierarchical;
+
+using ICSharpCode.ILSpyX.TreeView;
+
+namespace ILSpy.AssemblyTree
+{
+	public partial class AssemblyListPane : UserControl
+	{
+		public AssemblyListPane()
+		{
+			InitializeComponent();
+		}
+
+		protected override void OnDataContextChanged(System.EventArgs e)
+		{
+			base.OnDataContextChanged(e);
+
+			if (DataContext is AssemblyTreeModel model)
+			{
+				model.PropertyChanged += Model_PropertyChanged;
+				if (model.Root != null)
+					BindTree(model.Root);
+			}
+		}
+
+		void Model_PropertyChanged(object? sender, PropertyChangedEventArgs e)
+		{
+			if (e.PropertyName == nameof(AssemblyTreeModel.Root) && sender is AssemblyTreeModel model && model.Root != null)
+				BindTree(model.Root);
+		}
+
+		void BindTree(SharpTreeNode root)
+		{
+			var options = new HierarchicalOptions<SharpTreeNode> {
+				ChildrenSelector = node => node.Children,
+				IsLeafSelector = node => !node.ShowExpander,
+				IsExpandedSelector = node => node.IsExpanded,
+				IsExpandedSetter = (node, val) => node.IsExpanded = val,
+				AutoExpandRoot = true,
+			};
+
+			var hierarchicalModel = new HierarchicalModel<SharpTreeNode>(options);
+			hierarchicalModel.SetRoots((IEnumerable)root.Children);
+
+			TreeGrid.HierarchicalModel = hierarchicalModel;
+		}
+	}
+}

ILSpy/AssemblyTree/AssemblyTreeModel.cs

@@ -0,0 +1,79 @@
+// Copyright (c) 2026 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.Composition;
+
+using CommunityToolkit.Mvvm.ComponentModel;
+
+using ICSharpCode.ILSpyX;
+using ICSharpCode.ILSpyX.Settings;
+using ICSharpCode.ILSpyX.TreeView;
+
+using ILSpy.TreeNodes;
+
+namespace ILSpy.AssemblyTree
+{
+	[Export]
+	[Shared]
+	public partial class AssemblyTreeModel : ObservableObject
+	{
+		[ObservableProperty]
+		private SharpTreeNode? root;
+
+		[ObservableProperty]
+		private SharpTreeNode? selectedItem;
+
+		public AssemblyList? AssemblyList { get; private set; }
+
+		public void Initialize()
+		{
+			var settings = ILSpySettings.Load();
+			var listManager = new AssemblyListManager(settings);
+			listManager.CreateDefaultAssemblyLists();
+
+			AssemblyList = listManager.LoadList(AssemblyListManager.DefaultListName);
+
+			if (AssemblyList.GetAssemblies().Length == 0)
+				LoadInitialAssemblies(AssemblyList);
+
+			var rootNode = new AssemblyListTreeNode(AssemblyList);
+			rootNode.IsExpanded = true;
+			Root = rootNode;
+		}
+
+		static void LoadInitialAssemblies(AssemblyList assemblyList)
+		{
+			System.Reflection.Assembly[] initialAssemblies = {
+				typeof(object).Assembly,
+				typeof(Uri).Assembly,
+				typeof(System.Linq.Enumerable).Assembly,
+			};
+			foreach (var asm in initialAssemblies)
+			{
+				if (!string.IsNullOrEmpty(asm.Location))
+					assemblyList.OpenAssembly(asm.Location);
+			}
+		}
+
+		public void OpenAssembly(string path)
+		{
+			AssemblyList?.Open(path);
+		}
+	}
+}

ILSpy/TreeNodes/AssemblyListTreeNode.cs

@@ -0,0 +1,59 @@
+// Copyright (c) 2026 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.Specialized;
+using System.Linq;
+
+using ICSharpCode.ILSpyX;
+
+namespace ILSpy.TreeNodes
+{
+	sealed class AssemblyListTreeNode : ILSpyTreeNode
+	{
+		readonly AssemblyList assemblyList;
+
+		public AssemblyList AssemblyList => assemblyList;
+
+		public AssemblyListTreeNode(AssemblyList assemblyList)
+		{
+			ArgumentNullException.ThrowIfNull(assemblyList);
+			this.assemblyList = assemblyList;
+
+			Children.AddRange(assemblyList.GetAssemblies().Select(a => new AssemblyTreeNode(a)));
+
+			assemblyList.CollectionChanged += (_, e) => {
+				switch (e.Action)
+				{
+					case NotifyCollectionChangedAction.Add:
+						Children.InsertRange(e.NewStartingIndex, e.NewItems!.Cast<LoadedAssembly>().Select(a => new AssemblyTreeNode(a)));
+						break;
+					case NotifyCollectionChangedAction.Remove:
+						Children.RemoveRange(e.OldStartingIndex, e.OldItems!.Count);
+						break;
+					case NotifyCollectionChangedAction.Reset:
+						Children.Clear();
+						Children.AddRange(assemblyList.GetAssemblies().Select(a => new AssemblyTreeNode(a)));
+						break;
+				}
+			};
+		}
+
+		public override object Text => assemblyList.ListName;
+	}
+}

ILSpy/TreeNodes/AssemblyTreeNode.cs

@@ -0,0 +1,70 @@
+// Copyright (c) 2026 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.Linq;
+
+using ICSharpCode.Decompiler.Metadata;
+using ICSharpCode.ILSpyX;
+
+namespace ILSpy.TreeNodes
+{
+	sealed class AssemblyTreeNode : ILSpyTreeNode
+	{
+		readonly LoadedAssembly assembly;
+
+		public LoadedAssembly LoadedAssembly => assembly;
+
+		public AssemblyTreeNode(LoadedAssembly assembly)
+		{
+			ArgumentNullException.ThrowIfNull(assembly);
+			this.assembly = assembly;
+			LazyLoading = true;
+		}
+
+		public override object Text => assembly.ShortName;
+
+		protected override void LoadChildren()
+		{
+			var result = assembly.GetMetadataFileOrNullAsync().Result;
+			if (result is not MetadataFile module)
+				return;
+
+			var metadata = module.Metadata;
+			var namespaces = metadata.TypeDefinitions
+				.Where(t => metadata.GetTypeDefinition(t).GetDeclaringType().IsNil)
+				.Select(t => metadata.GetString(metadata.GetTypeDefinition(t).Namespace))
+				.Where(ns => !string.IsNullOrEmpty(ns))
+				.Distinct()
+				.OrderBy(ns => ns);
+
+			foreach (var ns in namespaces)
+				Children.Add(new NamespaceTreeNode(ns, module));
+
+			var globalTypes = metadata.TypeDefinitions
+				.Where(t => {
+					var td = metadata.GetTypeDefinition(t);
+					return td.GetDeclaringType().IsNil
+						&& string.IsNullOrEmpty(metadata.GetString(td.Namespace));
+				});
+
+			foreach (var t in globalTypes)
+				Children.Add(new TypeTreeNode(t, module));
+		}
+	}
+}

ILSpy/TreeNodes/ILSpyTreeNode.cs

@@ -0,0 +1,26 @@
+// Copyright (c) 2026 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 ICSharpCode.ILSpyX.TreeView;
+
+namespace ILSpy.TreeNodes
+{
+	public abstract class ILSpyTreeNode : SharpTreeNode
+	{
+	}
+}

ILSpy/TreeNodes/MemberTreeNode.cs

@@ -0,0 +1,33 @@
+// Copyright (c) 2026 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.
+
+namespace ILSpy.TreeNodes
+{
+	sealed class MemberTreeNode : ILSpyTreeNode
+	{
+		readonly string name;
+
+		public MemberTreeNode(string name)
+		{
+			this.name = name;
+		}
+
+		public override object Text => name;
+		public override bool ShowExpander => false;
+	}
+}

ILSpy/TreeNodes/NamespaceTreeNode.cs

@@ -0,0 +1,57 @@
+// Copyright (c) 2026 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.Linq;
+using System.Reflection.Metadata;
+
+using ICSharpCode.Decompiler.Metadata;
+
+namespace ILSpy.TreeNodes
+{
+	sealed class NamespaceTreeNode : ILSpyTreeNode
+	{
+		readonly string name;
+		readonly MetadataFile module;
+
+		public string Name => name;
+
+		public NamespaceTreeNode(string name, MetadataFile module)
+		{
+			this.name = name;
+			this.module = module;
+			LazyLoading = true;
+		}
+
+		public override object Text => name;
+
+		protected override void LoadChildren()
+		{
+			var metadata = module.Metadata;
+			var types = metadata.TypeDefinitions
+				.Where(t => {
+					var td = metadata.GetTypeDefinition(t);
+					return td.GetDeclaringType().IsNil
+						&& metadata.GetString(td.Namespace) == name;
+				})
+				.OrderBy(t => metadata.GetString(metadata.GetTypeDefinition(t).Name));
+
+			foreach (var t in types)
+				Children.Add(new TypeTreeNode(t, module));
+		}
+	}
+}

ILSpy/TreeNodes/TypeTreeNode.cs

@@ -0,0 +1,80 @@
+// Copyright (c) 2026 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.Linq;
+using System.Reflection.Metadata;
+
+using ICSharpCode.Decompiler.Metadata;
+
+namespace ILSpy.TreeNodes
+{
+	sealed class TypeTreeNode : ILSpyTreeNode
+	{
+		readonly TypeDefinitionHandle handle;
+		readonly MetadataFile module;
+
+		public TypeDefinitionHandle Handle => handle;
+		public MetadataFile Module => module;
+
+		public TypeTreeNode(TypeDefinitionHandle handle, MetadataFile module)
+		{
+			this.handle = handle;
+			this.module = module;
+			LazyLoading = true;
+		}
+
+		public override object Text {
+			get {
+				var td = module.Metadata.GetTypeDefinition(handle);
+				return module.Metadata.GetString(td.Name);
+			}
+		}
+
+		protected override void LoadChildren()
+		{
+			var td = module.Metadata.GetTypeDefinition(handle);
+
+			foreach (var nestedType in td.GetNestedTypes())
+				Children.Add(new TypeTreeNode(nestedType, module));
+
+			foreach (var method in td.GetMethods())
+			{
+				var md = module.Metadata.GetMethodDefinition(method);
+				Children.Add(new MemberTreeNode(module.Metadata.GetString(md.Name)));
+			}
+
+			foreach (var field in td.GetFields())
+			{
+				var fd = module.Metadata.GetFieldDefinition(field);
+				Children.Add(new MemberTreeNode(module.Metadata.GetString(fd.Name)));
+			}
+
+			foreach (var prop in td.GetProperties())
+			{
+				var pd = module.Metadata.GetPropertyDefinition(prop);
+				Children.Add(new MemberTreeNode(module.Metadata.GetString(pd.Name)));
+			}
+
+			foreach (var evt in td.GetEvents())
+			{
+				var ed = module.Metadata.GetEventDefinition(evt);
+				Children.Add(new MemberTreeNode(module.Metadata.GetString(ed.Name)));
+			}
+		}
+	}
+}

ILSpy/ViewModels/MainWindowViewModel.cs

@@ -18,16 +18,22 @@
 
 using System.Composition;
 
+using ILSpy.AssemblyTree;
+
 namespace ILSpy.ViewModels
 {
 	[Export]
 	[Shared]
 	public partial class MainWindowViewModel : ViewModelBase
 	{
-		public MainWindowViewModel()
-		{
-		}
+		public AssemblyTreeModel AssemblyTreeModel { get; }
 
 		public string Title => "ILSpy";
+
+		[ImportingConstructor]
+		public MainWindowViewModel(AssemblyTreeModel assemblyTreeModel)
+		{
+			AssemblyTreeModel = assemblyTreeModel;
+		}
 	}
 }

ILSpy/Views/MainWindow.axaml.cs

@@ -37,6 +37,7 @@ namespace ILSpy.Views
 		public MainWindow(MainWindowViewModel viewModel) : this()
 		{
 			DataContext = viewModel;
+			Opened += (_, _) => viewModel.AssemblyTreeModel.Initialize();
 		}
 	}
 }