Multi-selection in the assembly tree

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

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

ILSpy.Tests/AssemblyList/AssemblyTreeTests.cs

@@ -31,8 +31,12 @@ using ICSharpCode.ILSpy.Properties;
 using ICSharpCode.Decompiler.TypeSystem;
 using ICSharpCode.ILSpyX;
 
+using Avalonia.Controls;
+using Avalonia.VisualTree;
+
 using ILSpy;
 using ILSpy.AppEnv;
+using ILSpy.AssemblyTree;
 using ILSpy.Commands;
 using ILSpy.Images;
 using ILSpy.TreeNodes;
@@ -67,6 +71,49 @@ public class AssemblyTreeTests
 		resources.Children.Should().AllBeAssignableTo<ResourceTreeNode>();
 	}
 
+	[AvaloniaTest]
+	public async Task DataGrid_Has_Extended_Selection_Mode()
+	{
+		var window = AppComposition.Current.GetExport<MainWindow>();
+		window.Show();
+		var vm = (MainWindowViewModel)window.DataContext!;
+		await vm.AssemblyTreeModel.WaitForAssembliesAsync(minimumCount: 3);
+
+		var pane = await window.WaitForComponent<AssemblyListPane>();
+		var treeGrid = await pane.WaitForComponent<DataGrid>();
+		treeGrid.SelectionMode.Should().Be(DataGridSelectionMode.Extended,
+			"the assembly tree must let users Ctrl-click multiple rows");
+	}
+
+	[AvaloniaTest]
+	public async Task Multi_Selection_Tracks_Multiple_Nodes_And_Marks_Them_IsSelected()
+	{
+		var window = AppComposition.Current.GetExport<MainWindow>();
+		window.Show();
+		var vm = (MainWindowViewModel)window.DataContext!;
+		await vm.AssemblyTreeModel.WaitForAssembliesAsync(minimumCount: 3);
+
+		var typeNode = vm.AssemblyTreeModel.FindNode<TypeTreeNode>(
+			"System.Linq", "System.Linq", "System.Linq.Enumerable");
+		typeNode.EnsureLazyChildren();
+		var first = typeNode.Children.OfType<MethodTreeNode>()
+			.Single(m => m.MethodDefinition.Name == "AsEnumerable");
+		var second = typeNode.Children.OfType<MethodTreeNode>()
+			.First(m => m.MethodDefinition.Name == "Empty");
+
+		vm.AssemblyTreeModel.SelectedItems.Add(first);
+		vm.AssemblyTreeModel.SelectedItems.Add(second);
+
+		vm.AssemblyTreeModel.SelectedItems.Should().Contain(first);
+		vm.AssemblyTreeModel.SelectedItems.Should().Contain(second);
+		first.IsSelected.Should().BeTrue();
+		second.IsSelected.Should().BeTrue();
+
+		vm.AssemblyTreeModel.SelectedItems.Remove(first);
+		first.IsSelected.Should().BeFalse();
+		second.IsSelected.Should().BeTrue();
+	}
+
 	[AvaloniaTest]
 	public async Task Loading_Zip_Package_Surfaces_Folders_And_Entries()
 	{

ILSpy.Tests/Editor/DecompilerViewTests.cs

@@ -263,6 +263,57 @@ public class DecompilerViewTests
 		}
 	}
 
+	[AvaloniaTest]
+	public async Task Multi_Selection_Tab_Title_Joins_All_Selected_Names_With_Comma()
+	{
+		var window = AppComposition.Current.GetExport<MainWindow>();
+		window.Show();
+		var vm = (MainWindowViewModel)window.DataContext!;
+		await vm.AssemblyTreeModel.WaitForAssembliesAsync(minimumCount: 3);
+
+		var typeNode = vm.AssemblyTreeModel.FindNode<TypeTreeNode>(
+			"System.Linq", "System.Linq", "System.Linq.Enumerable");
+		typeNode.EnsureLazyChildren();
+		var asEnumerable = typeNode.Children.OfType<MethodTreeNode>()
+			.First(m => m.MethodDefinition.Name == "AsEnumerable");
+		var empty = typeNode.Children.OfType<MethodTreeNode>()
+			.First(m => m.MethodDefinition.Name == "Empty");
+
+		vm.AssemblyTreeModel.SelectedItems.Clear();
+		vm.AssemblyTreeModel.SelectedItems.Add(asEnumerable);
+		vm.AssemblyTreeModel.SelectedItems.Add(empty);
+
+		var tab = await vm.DockWorkspace.WaitForDecompiledTextAsync();
+		tab.Title.Should().Be($"{asEnumerable.Text}, {empty.Text}");
+	}
+
+	[AvaloniaTest]
+	public async Task Multi_Selecting_Methods_Decompiles_All_Of_Them_Into_One_View()
+	{
+		var window = AppComposition.Current.GetExport<MainWindow>();
+		window.Show();
+		var vm = (MainWindowViewModel)window.DataContext!;
+		await vm.AssemblyTreeModel.WaitForAssembliesAsync(minimumCount: 3);
+
+		var typeNode = vm.AssemblyTreeModel.FindNode<TypeTreeNode>(
+			"System.Linq", "System.Linq", "System.Linq.Enumerable");
+		typeNode.EnsureLazyChildren();
+		var asEnumerable = typeNode.Children.OfType<MethodTreeNode>()
+			.First(m => m.MethodDefinition.Name == "AsEnumerable");
+		var empty = typeNode.Children.OfType<MethodTreeNode>()
+			.First(m => m.MethodDefinition.Name == "Empty");
+
+		vm.AssemblyTreeModel.SelectedItems.Clear();
+		vm.AssemblyTreeModel.SelectedItems.Add(asEnumerable);
+		vm.AssemblyTreeModel.SelectedItems.Add(empty);
+
+		var tab = await vm.DockWorkspace.WaitForDecompiledTextAsync();
+		tab.Text.Should().Contain("AsEnumerable");
+		tab.Text.Should().Contain("Empty");
+		// Body fragment from AsEnumerable to confirm both bodies actually rendered.
+		tab.Text.Should().Contain("return source");
+	}
+
 	[AvaloniaTest]
 	public async Task Selecting_Assembly_Node_Emits_Header_And_Assembly_Attributes()
 	{

ILSpy.Tests/Waiters.cs

@@ -21,7 +21,9 @@ using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Threading.Tasks;
 
+using Avalonia;
 using Avalonia.Threading;
+using Avalonia.VisualTree;
 
 using global::ILSpy.AssemblyTree;
 using global::ILSpy.Docking;
@@ -66,6 +68,24 @@ public static class Waiters
 		await Task.WhenAll(assemblies.Select(a => a.GetLoadResultAsync()));
 	}
 
+	/// <summary>
+	/// Waits until exactly one descendant of <typeparamref name="T"/> exists in the
+	/// <paramref name="root"/>'s visual tree, then returns it. Replaces the brittle
+	/// <c>root.GetVisualDescendants().OfType&lt;T&gt;().Single()</c> pattern that races against
+	/// the layout/composition cycle - Avalonia.Headless tests routinely query the visual tree
+	/// before lazily-templated panes (DataGrid, dock panes, etc.) have materialised.
+	/// </summary>
+	public static async Task<T> WaitForComponent<T>(this Visual root, TimeSpan? timeout = null)
+		where T : Visual
+	{
+		ArgumentNullException.ThrowIfNull(root);
+		await WaitForAsync(
+			() => root.GetVisualDescendants().OfType<T>().Any(),
+			timeout,
+			$"a {typeof(T).Name} descendant to materialise in the visual tree");
+		return root.GetVisualDescendants().OfType<T>().First();
+	}
+
 	public static async Task<DecompilerTabPageModel> WaitForDecompiledTextAsync(
 		this DockWorkspace dock,
 		TimeSpan? timeout = null)

ILSpy/AssemblyTree/AssemblyListPane.axaml

@@ -20,7 +20,7 @@
 	          GridLinesVisibility="None"
 	          IsReadOnly="True"
 	          CanUserResizeColumns="False"
-	          SelectionMode="Single"
+	          SelectionMode="Extended"
 	          SelectionChanged="OnTreeGridSelectionChanged">
 		<DataGrid.Columns>
 			<DataGridHierarchicalColumn Header="Name" Width="*"

ILSpy/AssemblyTree/AssemblyListPane.axaml.cs

@@ -50,14 +50,34 @@ namespace ILSpy.AssemblyTree
 		{
 			if (syncingSelection || DataContext is not AssemblyTreeModel model)
 				return;
-			SharpTreeNode? selected = null;
+			// SelectedItem is a wrapper over SelectedItems on the model — touching it would
-			if (TreeGrid.SelectedItem is HierarchicalNode node && node.Item is SharpTreeNode tree)
+			// Clear+Add and clobber Ctrl-click multi-selection. Only mutate the collection.
-				selected = tree;
+			BeginSync();
-			else if (TreeGrid.SelectedItem is SharpTreeNode direct)
+			try
-				selected = direct;
+			{
-			if (model.SelectedItem == selected)
+				var current = new System.Collections.Generic.HashSet<SharpTreeNode>();
-				return;
+				foreach (var item in TreeGrid.SelectedItems)
-			model.SelectedItem = selected;
+				{
+					var node = item is HierarchicalNode hn && hn.Item is SharpTreeNode t ? t
+						: item as SharpTreeNode;
+					if (node != null)
+						current.Add(node);
+				}
+				for (int i = model.SelectedItems.Count - 1; i >= 0; i--)
+				{
+					if (!current.Contains(model.SelectedItems[i]))
+						model.SelectedItems.RemoveAt(i);
+				}
+				foreach (var node in current)
+				{
+					if (!model.SelectedItems.Contains(node))
+						model.SelectedItems.Add(node);
+				}
+			}
+			finally
+			{
+				EndSync();
+			}
 		}
 
 		void SyncSelectionFromModel(SharpTreeNode? target)

ILSpy/AssemblyTree/AssemblyTreeModel.cs

@@ -19,6 +19,7 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
+using System.Collections.Specialized;
 using System.Composition;
 using System.Linq;
 using System.Reflection.Metadata.Ecma335;
@@ -54,9 +55,34 @@ namespace ILSpy.AssemblyTree
 		[property: IgnoreDataMember]
 		private SharpTreeNode? root;
 
-		[ObservableProperty]
+		/// <summary>
-		[property: IgnoreDataMember]
+		/// Multi-selection set. Each entry is kept in sync with its
-		private SharpTreeNode? selectedItem;
+		/// <see cref="SharpTreeNode.IsSelected"/>. <see cref="SelectedItem"/> is a convenience
+		/// wrapper around the *primary* (last-added) entry — drives decompilation, navigation
+		/// history, and tree-view-path persistence — but the underlying state is single-sourced
+		/// here, mirroring the WPF host's MultiSelectorExtensions.SelectionBinding pattern.
+		/// </summary>
+		[IgnoreDataMember]
+		public ObservableCollection<SharpTreeNode> SelectedItems { get; } = [];
+
+		/// <summary>
+		/// Primary (last) selection. Get returns the most recently selected entry of
+		/// <see cref="SelectedItems"/>, or <c>null</c>; set replaces the entire selection
+		/// with the supplied node (clears the collection then adds it). All
+		/// <c>PropertyChanged(SelectedItem)</c> notifications are fired by
+		/// <see cref="SelectedItems.CollectionChanged"/>.
+		/// </summary>
+		[IgnoreDataMember]
+		public SharpTreeNode? SelectedItem {
+			get => SelectedItems.Count > 0 ? SelectedItems[^1] : null;
+			set {
+				if (SelectedItem == value)
+					return;
+				SelectedItems.Clear();
+				if (value != null)
+					SelectedItems.Add(value);
+			}
+		}
 
 		[ObservableProperty]
 		[property: IgnoreDataMember]
@@ -77,11 +103,27 @@ namespace ILSpy.AssemblyTree
 				if (e.PropertyName == nameof(LanguageService.CurrentLanguage) && Root != null)
 					NotifyTextChanged(Root);
 			};
+			SelectedItems.CollectionChanged += OnSelectedItemsChanged;
 			Id = PaneContentId;
 			Title = "Assemblies";
 			CanClose = false;
 		}
 
+		void OnSelectedItemsChanged(object? sender, NotifyCollectionChangedEventArgs e)
+		{
+			if (e.NewItems != null)
+				foreach (SharpTreeNode n in e.NewItems)
+					n.IsSelected = true;
+			if (e.OldItems != null)
+				foreach (SharpTreeNode n in e.OldItems)
+					n.IsSelected = false;
+
+			// SelectedItem is a wrapper over this collection — anyone bound to it must be
+			// notified, and the saved path must follow the new primary.
+			OnPropertyChanged(nameof(SelectedItem));
+			settingsService.SessionSettings.ActiveTreeViewPath = GetPathForNode(SelectedItem);
+		}
+
 		// Walks already-materialized children and re-raises Text PropertyChanged so the cell
 		// templates pick up the new language's formatting -- without collapsing the user's
 		// expanded state. Lazy-loaded subtrees that haven't been opened yet are skipped (they'll
@@ -137,15 +179,6 @@ namespace ILSpy.AssemblyTree
 			}
 		}
 
-		partial void OnSelectedItemChanged(SharpTreeNode? oldValue, SharpTreeNode? newValue)
-		{
-			if (oldValue != null)
-				oldValue.IsSelected = false;
-			if (newValue != null)
-				newValue.IsSelected = true;
-			settingsService.SessionSettings.ActiveTreeViewPath = GetPathForNode(newValue);
-		}
-
 		void ShowAssemblyList(string name)
 		{
 			if (listManager == null)

ILSpy/Docking/DockWorkspace.cs

@@ -20,6 +20,7 @@ using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Composition;
+using System.Linq;
 
 using CommunityToolkit.Mvvm.Input;
 
@@ -82,6 +83,7 @@ namespace ILSpy.Docking
 			}
 
 			assemblyTreeModel.PropertyChanged += OnAssemblyTreePropertyChanged;
+			assemblyTreeModel.SelectedItems.CollectionChanged += (_, _) => ShowSelectedNode();
 			languageService.PropertyChanged += OnLanguagePropertyChanged;
 			// Layout/factory initialization (locators, parent/factory wiring) is done by
 			// the DockControl in MainWindow.axaml via InitializeFactory/InitializeLayout.
@@ -201,7 +203,8 @@ namespace ILSpy.Docking
 
 		void ShowSelectedNode()
 		{
-			if (assemblyTreeModel.SelectedItem is not ILSpyTreeNode node)
+			var nodes = assemblyTreeModel.SelectedItems.OfType<ILSpyTreeNode>().ToArray();
+			if (nodes.Length == 0)
 				return;
 			var tab = GetActiveDecompilerTab();
 			if (tab == null)
@@ -214,7 +217,7 @@ namespace ILSpy.Docking
 				factory.SetFocusedDockable(factory.Documents, tab);
 			}
 			tab.Language = languageService.CurrentLanguage;
-			tab.CurrentNode = node;
+			tab.CurrentNodes = nodes;
 		}
 
 		DecompilerTabPageModel? GetActiveDecompilerTab()

ILSpy/TextView/DecompilerTabPageModel.cs

@@ -19,6 +19,7 @@
 using System;
 using System.Collections.Generic;
 using System.ComponentModel;
+using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 
@@ -108,7 +109,7 @@ namespace ILSpy.TextView
 		internal void RaiseNavigateRequested(ReferenceSegment segment)
 			=> NavigateRequested?.Invoke(segment);
 
-		ILSpyTreeNode? currentNode;
+		IReadOnlyList<ILSpyTreeNode> currentNodes = System.Array.Empty<ILSpyTreeNode>();
 
 		[RelayCommand]
 		void CancelDecompilation()
@@ -116,16 +117,33 @@ namespace ILSpy.TextView
 			activeCts?.Cancel();
 		}
 
+		/// <summary>
+		/// Single-selection convenience wrapper over <see cref="CurrentNodes"/> — get returns
+		/// the first node (or null), set replaces the list with the single node.
+		/// </summary>
 		public ILSpyTreeNode? CurrentNode {
-			get => currentNode;
+			get => currentNodes.Count > 0 ? currentNodes[0] : null;
+			set => CurrentNodes = value == null
+				? System.Array.Empty<ILSpyTreeNode>()
+				: new[] { value };
+		}
+
+		/// <summary>
+		/// All tree nodes whose decompiled output appears in this tab. Setting fires a fresh
+		/// <see cref="DecompileAsync"/> that iterates each node and writes its output, blank
+		/// line in between. The first node drives the tab title.
+		/// </summary>
+		public IReadOnlyList<ILSpyTreeNode> CurrentNodes {
+			get => currentNodes;
 			set {
-				if (currentNode == value)
+				ArgumentNullException.ThrowIfNull(value);
+				if (currentNodes.SequenceEqual(value))
 					return;
-				if (currentNode != null)
+				foreach (var n in currentNodes)
-					currentNode.PropertyChanged -= OnCurrentNodePropertyChanged;
+					n.PropertyChanged -= OnCurrentNodePropertyChanged;
-				currentNode = value;
+				currentNodes = value.ToArray();
-				if (currentNode != null)
+				foreach (var n in currentNodes)
-					currentNode.PropertyChanged += OnCurrentNodePropertyChanged;
+					n.PropertyChanged += OnCurrentNodePropertyChanged;
 				_ = DecompileAsync();
 			}
 		}
@@ -136,10 +154,17 @@ namespace ILSpy.TextView
 			// from ShortName to "ShortName (version, tfm)" once the assembly finishes loading).
 			// While a decompile is running the spinner prefixes the title — keep the prefix and
 			// just refresh the suffix; otherwise replace the title outright.
-			if (e.PropertyName != nameof(ILSpyTreeNode.Text) || sender is not ILSpyTreeNode node)
+			if (e.PropertyName != nameof(ILSpyTreeNode.Text))
 				return;
-			var text = node.Text?.ToString() ?? "(unnamed)";
+			var baseTitle = ComposeBaseTitle();
-			Title = IsDecompiling ? ComposeSpinnerTitle(0, text) : text;
+			Title = IsDecompiling ? ComposeSpinnerTitle(0, baseTitle) : baseTitle;
+		}
+
+		string ComposeBaseTitle()
+		{
+			if (currentNodes.Count == 0)
+				return "(unnamed)";
+			return string.Join(", ", currentNodes.Select(n => n.Text?.ToString() ?? "(unnamed)"));
 		}
 
 		// Resolved lazily so unit tests / design-time previews that bypass the composition host
@@ -166,9 +191,9 @@ namespace ILSpy.TextView
 		{
 			activeCts?.Cancel();
 			var cts = activeCts = new CancellationTokenSource();
-			var node = currentNode;
+			var nodes = currentNodes;
 			var language = Language;
-			if (node == null || language == null)
+			if (nodes.Count == 0 || language == null)
 			{
 				Text = string.Empty;
 				IsDecompiling = false;
@@ -180,7 +205,7 @@ namespace ILSpy.TextView
 
 			// Spinner appears as a glyph prefix on the tab title while the decompile runs;
 			// editor state is left untouched so cancellation falls back cleanly.
-			Title = ComposeSpinnerTitle(0, currentNode?.Text?.ToString() ?? "(unnamed)");
+			Title = ComposeSpinnerTitle(0, ComposeBaseTitle());
 			TaskbarProgress?.SetState(TaskbarProgressState.Indeterminate);
 			_ = RunSpinnerAsync(cts.Token);
 
@@ -191,7 +216,14 @@ namespace ILSpy.TextView
 					var options = new DecompilationOptions { CancellationToken = cts.Token };
 					try
 					{
-						node.Decompile(language, output, options);
+						for (int i = 0; i < nodes.Count; i++)
+						{
+							if (cts.Token.IsCancellationRequested)
+								break;
+							if (i > 0)
+								output.WriteLine();
+							nodes[i].Decompile(language, output, options);
+						}
 					}
 					catch (OperationCanceledException)
 					{
@@ -220,7 +252,7 @@ namespace ILSpy.TextView
 					// Re-read Text now (instead of capturing it before decompile started) — for
 					// freshly-opened assemblies, Text only has the rich "(version, tfm)" form
 					// after the load completes during decompile.
-					Title = currentNode?.Text?.ToString() ?? "(unnamed)";
+					Title = ComposeBaseTitle();
 					SyntaxExtension = newSyntaxExtension;
 					HighlightingModel = model;
 					Foldings = collectedFoldings;
@@ -247,8 +279,8 @@ namespace ILSpy.TextView
 						IsDecompiling = false;
 						// If we cancelled before producing fresh output, drop the spinner glyph
 						// from the title — the editor still shows the previous decompile.
-						if (currentNode != null)
+						if (currentNodes.Count > 0)
-							Title = currentNode.Text?.ToString() ?? "(unnamed)";
+							Title = ComposeBaseTitle();
 						TaskbarProgress?.SetState(TaskbarProgressState.None);
 					}
 					if (Dispatcher.UIThread.CheckAccess())
@@ -282,7 +314,7 @@ namespace ILSpy.TextView
 				}
 				if (token.IsCancellationRequested || !IsDecompiling)
 					return;
-				Title = ComposeSpinnerTitle(frame++, currentNode?.Text?.ToString() ?? "(unnamed)");
+				Title = ComposeSpinnerTitle(frame++, ComposeBaseTitle());
 			}
 		}
 	}