Enable separate language (version) settings per document.

ILSpy/Commands/DecompileInNewViewCommand.cs

@@ -55,7 +55,7 @@ namespace ICSharpCode.ILSpy.Commands
 		private static void DecompileNodes(params ILSpyTreeNode[] nodes)
 		{
 			var title = string.Join(", ", nodes.Select(x => x.ToString()));
-			DockWorkspace.Instance.Documents.Add(new ViewModels.DecompiledDocumentModel(title, title));
+			DockWorkspace.Instance.Documents.Add(new ViewModels.DecompiledDocumentModel(title, title) { Language = MainWindow.Instance.CurrentLanguage, LanguageVersion = MainWindow.Instance.CurrentLanguageVersion });
 			DockWorkspace.Instance.ActiveDocument = DockWorkspace.Instance.Documents.Last();
 			MainWindow.Instance.Dispatcher.BeginInvoke(System.Windows.Threading.DispatcherPriority.Background, (Action)delegate {
 				DockWorkspace.Instance.GetTextView().DecompileAsync(MainWindow.Instance.CurrentLanguage, nodes, new DecompilationOptions());

ILSpy/Docking/DockWorkspace.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.ObjectModel;
 using System.ComponentModel;
+using System.Runtime.CompilerServices;
 using System.Threading;
 using System.Threading.Tasks;
 using ICSharpCode.AvalonEdit.Highlighting;
@@ -11,6 +12,8 @@ namespace ICSharpCode.ILSpy.Docking
 {
 	public class DockWorkspace : INotifyPropertyChanged
 	{
+		private SessionSettings sessionSettings;
+
 		public event PropertyChangedEventHandler PropertyChanged;
 
 		public static DockWorkspace Instance { get; } = new DockWorkspace();
@@ -37,12 +40,16 @@ namespace ICSharpCode.ILSpy.Docking
 			set {
 				if (_activeDocument != value) {
 					_activeDocument = value;
+					if (value is DecompiledDocumentModel ddm) {
+						this.sessionSettings.FilterSettings.Language = ddm.Language;
+						this.sessionSettings.FilterSettings.LanguageVersion = ddm.LanguageVersion;
+					}
 					RaisePropertyChanged(nameof(ActiveDocument));
 				}
 			}
 		}
 
-		protected void RaisePropertyChanged(string propertyName)
+		protected void RaisePropertyChanged([CallerMemberName] string propertyName = null)
 		{
 			PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
 		}
@@ -71,5 +78,21 @@ namespace ICSharpCode.ILSpy.Docking
 		{
 			GetTextView().ShowNodes(output, nodes, highlighting);
 		}
+
+		internal void LoadSettings(SessionSettings sessionSettings)
+		{
+			this.sessionSettings = sessionSettings;
+			sessionSettings.FilterSettings.PropertyChanged += FilterSettings_PropertyChanged;
+		}
+
+		private void FilterSettings_PropertyChanged(object sender, PropertyChangedEventArgs e)
+		{
+			if (ActiveDocument is DecompiledDocumentModel ddm) {
+				if (e.PropertyName == "Language" || e.PropertyName == "LanguageVersion") {
+					ddm.Language = sessionSettings.FilterSettings.Language;
+					ddm.LanguageVersion = sessionSettings.FilterSettings.LanguageVersion;
+				}
+			}
+		}
 	}
 }

ILSpy/MainWindow.xaml.cs

@@ -122,6 +122,8 @@ namespace ICSharpCode.ILSpy
 				SessionSettings = sessionSettings
 			};
 
+			DockWorkspace.Instance.LoadSettings(sessionSettings);
+
 			InitializeComponent();
 
 			sessionSettings.DockLayout.Deserialize(new XmlLayoutSerializer(DockManager));
@@ -461,7 +463,7 @@ namespace ICSharpCode.ILSpy
 		void MainWindow_Loaded(object sender, RoutedEventArgs e)
 		{
 			DockWorkspace.Instance.ToolPanes.Add(AssemblyListPaneModel.Instance);
-			DockWorkspace.Instance.Documents.Add(new DecompiledDocumentModel() { IsCloseable = false });
+			DockWorkspace.Instance.Documents.Add(new DecompiledDocumentModel() { IsCloseable = false, Language = CurrentLanguage, LanguageVersion = CurrentLanguageVersion });
 			DockWorkspace.Instance.ActiveDocument = DockWorkspace.Instance.Documents.First();
 
 			ILSpySettings spySettings = this.spySettingsForMainWindow_Loaded;

ILSpy/ViewModels/DocumentModel.cs

@@ -36,5 +36,27 @@ namespace ICSharpCode.ILSpy.ViewModels
 				}
 			}
 		}
+
+		private Language language;
+		public Language Language {
+			get => language;
+			set {
+				if (language != value) {
+					language = value;
+					RaisePropertyChanged(nameof(Language));
+				}
+			}
+		}
+
+		private LanguageVersion languageVersion;
+		public LanguageVersion LanguageVersion {
+			get => languageVersion;
+			set {
+				if (languageVersion != value) {
+					languageVersion = value;
+					RaisePropertyChanged(nameof(LanguageVersion));
+				}
+			}
+		}
 	}
-}
+}