Replace ITextEditorProvider with GetService<ITextEditor>().

src/AddIns/BackendBindings/FSharpBinding/FSharpInteractive.cs

@@ -142,9 +142,8 @@ namespace FSharpBinding
 			pad.BringPadToFront();
 			FSharpInteractive fsharpInteractive = (FSharpInteractive)pad.PadContent;
 			if (fsharpInteractive.foundCompiler) {
-				ITextEditorProvider editorProvider = WorkbenchSingleton.Workbench.ActiveViewContent as ITextEditorProvider;
-				if (editorProvider != null) {
-					var textEditor = editorProvider.TextEditor;
+				ITextEditor textEditor = SD.GetActiveViewContentService<ITextEditor>();
+				if (textEditor != null) {
 					if (textEditor.SelectionLength > 0) {
 						fsharpInteractive.fsiProcess.StandardInput.WriteLine(textEditor.SelectedText);
 					} else {

src/AddIns/Debugger/Debugger.AddIn/DisableBreakpointMenuCommand.cs

@@ -21,13 +21,15 @@ namespace Debugger.AddIn
 	{
 		public override void Run()
 		{
-			ITextEditorProvider provider = WorkbenchSingleton.Workbench.ActiveWorkbenchWindow.ActiveViewContent as ITextEditorProvider;
+			ITextEditor editor = SD.GetActiveViewContentService<ITextEditor>();
+			if (editor == null)
+				return;
 			
 			BreakpointBookmark point = null;
 			
 			foreach (BreakpointBookmark breakpoint in DebuggerService.Breakpoints) {
-				if ((breakpoint.FileName == provider.TextEditor.FileName) &&
-				    (breakpoint.LineNumber == provider.TextEditor.Caret.Line)) {
+				if ((breakpoint.FileName == editor.FileName) &&
+				    (breakpoint.LineNumber == editor.Caret.Line)) {
 					point = breakpoint;
 					break;
 				}

src/AddIns/Debugger/Debugger.AddIn/EnableBreakpointMenuCommand.cs

@@ -21,13 +21,15 @@ namespace Debugger.AddIn
 	{
 		public override void Run()
 		{
-			ITextEditorProvider provider = WorkbenchSingleton.Workbench.ActiveWorkbenchWindow.ActiveViewContent as ITextEditorProvider;
+			ITextEditor editor = SD.GetActiveViewContentService<ITextEditor>();
+			if (editor == null)
+				return;
 			
 			BreakpointBookmark point = null;
 			
 			foreach (BreakpointBookmark breakpoint in DebuggerService.Breakpoints) {
-				if ((breakpoint.FileName == provider.TextEditor.FileName) &&
-				    (breakpoint.LineNumber == provider.TextEditor.Caret.Line)) {
+				if ((breakpoint.FileName == editor.FileName) &&
+				    (breakpoint.LineNumber == editor.Caret.Line)) {
 					point = breakpoint;
 					break;
 				}

src/AddIns/Debugger/Debugger.AddIn/IsActiveBreakpointCondition.cs

@@ -25,19 +25,17 @@ namespace Debugger.AddIn
 		
 		public bool IsValid(object caller, Condition condition)
 		{
-			if (WorkbenchSingleton.Workbench == null || WorkbenchSingleton.Workbench.ActiveWorkbenchWindow == null)
+			ITextEditor editor = SD.GetActiveViewContentService<ITextEditor>();
+			if (editor == null)
 				return false;
-			ITextEditorProvider provider = WorkbenchSingleton.Workbench.ActiveWorkbenchWindow.ActiveViewContent as ITextEditorProvider;
-			if (provider == null)
-				return false;
-			if (string.IsNullOrEmpty(provider.TextEditor.FileName))
+			if (string.IsNullOrEmpty(editor.FileName))
 				return false;
 			
 			BreakpointBookmark point = null;
 			
 			foreach (BreakpointBookmark breakpoint in DebuggerService.Breakpoints) {
-				if ((breakpoint.FileName == provider.TextEditor.FileName) &&
-				    (breakpoint.LineNumber == provider.TextEditor.Caret.Line)) {
+				if ((breakpoint.FileName == editor.FileName) &&
+				    (breakpoint.LineNumber == editor.Caret.Line)) {
 					point = breakpoint;
 					break;
 				}

src/AddIns/Debugger/Debugger.AddIn/IsBreakpointCondition.cs

@@ -25,17 +25,15 @@ namespace Debugger.AddIn
 		
 		public bool IsValid(object caller, Condition condition)
 		{
-			if (WorkbenchSingleton.Workbench == null || WorkbenchSingleton.Workbench.ActiveWorkbenchWindow == null)
+			ITextEditor editor = SD.GetActiveViewContentService<ITextEditor>();
+			if (editor == null)
 				return false;
-			ITextEditorProvider provider = WorkbenchSingleton.Workbench.ActiveWorkbenchWindow.ActiveViewContent as ITextEditorProvider;
-			if (provider == null)
-				return false;
-			if (string.IsNullOrEmpty(provider.TextEditor.FileName))
+			if (string.IsNullOrEmpty(editor.FileName))
 				return false;
 			
 			foreach (BreakpointBookmark mark in DebuggerService.Breakpoints) {
-				if ((mark.FileName == provider.TextEditor.FileName) &&
-				    (mark.LineNumber == provider.TextEditor.Caret.Line))
+				if ((mark.FileName == editor.FileName) &&
+				    (mark.LineNumber == editor.Caret.Line))
 					return true;
 			}
 			

src/AddIns/Debugger/Debugger.AddIn/Service/RunToCursorCommand.cs

@@ -14,13 +14,10 @@ namespace ICSharpCode.SharpDevelop.Services
 	{
 		public override void Run()
 		{
-			ITextEditorProvider provider = WorkbenchSingleton.Workbench.ActiveViewContent as ITextEditorProvider;
-			
-			if (provider == null || WindowsDebugger.CurrentProcess == null)
+			ITextEditor editor = SD.GetActiveViewContentService<ITextEditor>();
+			if (editor == null || WindowsDebugger.CurrentProcess == null)
 				return;
-			
-			ITextEditor textEditor = provider.TextEditor;
-			WindowsDebugger.CurrentProcess.RunTo(textEditor.FileName, textEditor.Caret.Line, textEditor.Caret.Column);
+			WindowsDebugger.CurrentProcess.RunTo(editor.FileName, editor.Caret.Line, editor.Caret.Column);
 		}
 	}
 }

src/AddIns/Debugger/Debugger.AddIn/Service/SetCurrentStatementCommand.cs

@@ -12,13 +12,11 @@ namespace ICSharpCode.SharpDevelop.Services
 	{
 		public override void Run()
 		{
-			ITextEditorProvider provider = WorkbenchSingleton.Workbench.ActiveViewContent as ITextEditorProvider;
+			ITextEditor textEditor = SD.GetActiveViewContentService<ITextEditor>();
 				
-			if (provider == null || DebuggerService.CurrentDebugger == null)
+			if (textEditor == null || DebuggerService.CurrentDebugger == null)
 				return;
 			
-			ITextEditor textEditor = provider.TextEditor;
-			
 			DebuggerService.CurrentDebugger.SetInstructionPointer(textEditor.FileName, textEditor.Caret.Line, textEditor.Caret.Column, false);
 		}
 	}

src/AddIns/DisplayBindings/AvalonEdit.AddIn/Src/AvalonEditViewContent.cs

@@ -22,8 +22,10 @@ using ICSharpCode.SharpDevelop.Project;
 
 namespace ICSharpCode.AvalonEdit.AddIn
 {
+	[ViewContentService]
 	public interface ICodeEditorProvider : ITextEditorProvider
 	{
+		[Obsolete("Use viewContent.GetService<CodeEditor>() instead.")]
 		CodeEditor CodeEditor { get; }
 	}
 	

src/AddIns/DisplayBindings/AvalonEdit.AddIn/Src/CodeEditor.cs

@@ -37,7 +37,7 @@ namespace ICSharpCode.AvalonEdit.AddIn
 	/// Integrates AvalonEdit with SharpDevelop.
 	/// Also provides support for Split-View (showing two AvalonEdit instances using the same TextDocument)
 	/// </summary>
-	[TextEditorService]
+	[TextEditorService, ViewContentService]
 	public class CodeEditor : Grid, IDisposable
 	{
 		const string contextMenuPath = "/SharpDevelop/ViewContent/AvalonEdit/ContextMenu";

src/AddIns/DisplayBindings/AvalonEdit.AddIn/Src/Commands/FoldingCommands.cs

@@ -15,8 +15,7 @@ namespace ICSharpCode.AvalonEdit.AddIn.Commands
 	{
 		public override void Run()
 		{
-			ITextEditorProvider provider = WorkbenchSingleton.Workbench.ActiveViewContent as ITextEditorProvider;
-			ITextEditor editor = provider.TextEditor;
+			ITextEditor editor = SD.GetActiveViewContentService<ITextEditor>();
 			FoldingManager foldingManager = editor.GetService(typeof(FoldingManager)) as FoldingManager;
 			
 			if (foldingManager != null) {
@@ -37,8 +36,7 @@ namespace ICSharpCode.AvalonEdit.AddIn.Commands
 	{
 		public override void Run()
 		{
-			ITextEditorProvider provider = WorkbenchSingleton.Workbench.ActiveViewContent as ITextEditorProvider;
-			ITextEditor editor = provider.TextEditor;
+			ITextEditor editor = SD.GetActiveViewContentService<ITextEditor>();
 			FoldingManager foldingManager = editor.GetService(typeof(FoldingManager)) as FoldingManager;
 			
 			if (foldingManager != null) {
@@ -60,8 +58,7 @@ namespace ICSharpCode.AvalonEdit.AddIn.Commands
 	{
 		public override void Run()
 		{
-			ITextEditorProvider provider = WorkbenchSingleton.Workbench.ActiveViewContent as ITextEditorProvider;
-			ITextEditor editor = provider.TextEditor;
+			ITextEditor editor = SD.GetActiveViewContentService<ITextEditor>();
 			FoldingManager foldingManager = editor.GetService(typeof(FoldingManager)) as FoldingManager;
 			
 			if (foldingManager != null) {

src/AddIns/DisplayBindings/AvalonEdit.AddIn/Src/Commands/SaveFileWithEncoding.cs

@@ -15,13 +15,15 @@ namespace ICSharpCode.AvalonEdit.AddIn.Commands
 		public override void Run()
 		{
 			IViewContent vc = WorkbenchSingleton.Workbench.ActiveViewContent;
-			ICodeEditorProvider cep = vc as ICodeEditorProvider;
-			if (cep != null) {
+			if (vc == null)
+				return;
+			var codeEditor = vc.GetService<CodeEditor>();
+			if (codeEditor != null) {
 				ChooseEncodingDialog dlg = new ChooseEncodingDialog();
 				dlg.Owner = WorkbenchSingleton.MainWindow;
-				dlg.Encoding = cep.CodeEditor.PrimaryTextEditor.Encoding;
+				dlg.Encoding = codeEditor.PrimaryTextEditor.Encoding;
 				if (dlg.ShowDialog() == true) {
-					cep.CodeEditor.PrimaryTextEditor.Encoding = dlg.Encoding;
+					codeEditor.PrimaryTextEditor.Encoding = dlg.Encoding;
 					SharpDevelop.Commands.SaveFile.Save(vc.PrimaryFile);
 				}
 			}

src/AddIns/DisplayBindings/AvalonEdit.AddIn/Src/Commands/SortSelectionCommand.cs

@@ -2,12 +2,14 @@
 // This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
 
 using System;
+using System.Collections.Generic;
 using System.Linq;
+
 using ICSharpCode.Core;
 using ICSharpCode.NRefactory.Editor;
+using ICSharpCode.SharpDevelop;
 using ICSharpCode.SharpDevelop.Editor;
 using ICSharpCode.SharpDevelop.Gui;
-using System.Collections.Generic;
 
 namespace ICSharpCode.AvalonEdit.AddIn.Commands
 {
@@ -24,9 +26,8 @@ namespace ICSharpCode.AvalonEdit.AddIn.Commands
 				if (SortOptions.SortDirection == SortDirection.Descending)
 					comparer = new DescendingStringComparer(comparer);
 				
-				ITextEditorProvider provider = WorkbenchSingleton.Workbench.ActiveViewContent as ITextEditorProvider;
-				if (provider != null) {
-					ITextEditor editor = provider.TextEditor;
+				ITextEditor editor = SD.GetActiveViewContentService<ITextEditor>();
+				if (editor != null) {
 					if (editor.SelectionLength > 0) {
 						int start = editor.Document.GetLineByOffset(editor.SelectionStart).LineNumber;
 						int end = editor.Document.GetLineByOffset(editor.SelectionStart + editor.SelectionLength).LineNumber;

src/AddIns/DisplayBindings/AvalonEdit.AddIn/Src/Commands/SurroundWithCommand.cs

@@ -4,10 +4,10 @@
 using System;
 using System.IO;
 using System.Linq;
-
 using ICSharpCode.AvalonEdit.AddIn.Snippets;
 using ICSharpCode.AvalonEdit.Editing;
 using ICSharpCode.Core;
+using ICSharpCode.SharpDevelop;
 using ICSharpCode.SharpDevelop.Editor;
 using ICSharpCode.SharpDevelop.Editor.CodeCompletion;
 using ICSharpCode.SharpDevelop.Gui;
@@ -21,21 +21,20 @@ namespace ICSharpCode.AvalonEdit.AddIn.Commands
 		/// </summary>
 		public override void Run()
 		{
-			ICodeEditorProvider provider = WorkbenchSingleton.Workbench.ActiveViewContent as ICodeEditorProvider;
-			
-			if (provider == null)
+			ITextEditor editor = SD.GetActiveViewContentService<ITextEditor>();
+			if (editor == null)
 				return;
 			
-			CodeSnippetGroup group = SnippetManager.Instance.FindGroup(Path.GetExtension(provider.TextEditor.FileName));
+			CodeSnippetGroup group = SnippetManager.Instance.FindGroup(Path.GetExtension(editor.FileName));
 			
 			if (group == null)
 				return;
 			
 			DefaultCompletionItemList list = new DefaultCompletionItemList();
 			
-			list.Items.AddRange(group.Snippets.Where(i => i.HasSelection).Select(item => item.CreateCompletionItem(provider.TextEditor)));
+			list.Items.AddRange(group.Snippets.Where(i => i.HasSelection).Select(item => item.CreateCompletionItem(editor)));
 			
-			new CodeSnippetCompletionWindow(provider.TextEditor, list).Show();
+			new CodeSnippetCompletionWindow(editor, list).Show();
 		}
 	}
 }

src/AddIns/DisplayBindings/AvalonEdit.AddIn/Src/ContextActions/ContextActionsPopup.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Windows.Controls.Primitives;
 using ICSharpCode.NRefactory.TypeSystem;
+using ICSharpCode.SharpDevelop;
 using ICSharpCode.SharpDevelop.Editor;
 using ICSharpCode.SharpDevelop.Gui;
 
@@ -61,12 +62,7 @@ namespace ICSharpCode.AvalonEdit.AddIn.ContextActions
 
 		ITextEditor GetCurrentEditor()
 		{
-			if (WorkbenchSingleton.Workbench == null)
-				return null;
-			var activeViewContent = WorkbenchSingleton.Workbench.ActiveViewContent as ITextEditorProvider;
-			if (activeViewContent == null)
-				return null;
-			return activeViewContent.TextEditor;
+			return SD.GetActiveViewContentService<ITextEditor>();
 		}
 		
 		void OpenAtMousePosition()

src/AddIns/DisplayBindings/XmlEditor/Project/Src/FormatXmlCommand.cs

@@ -1,10 +1,10 @@
 // Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
 // This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
 
-using ICSharpCode.SharpDevelop.Editor;
 using System;
 using ICSharpCode.Core;
-using ICSharpCode.SharpDevelop.Gui;
+using ICSharpCode.SharpDevelop;
+using ICSharpCode.SharpDevelop.Editor;
 
 namespace ICSharpCode.XmlEditor
 {
@@ -15,10 +15,9 @@ namespace ICSharpCode.XmlEditor
 	{
 		public override void Run()
 		{
-			ITextEditorProvider provider = WorkbenchSingleton.Workbench.ActiveViewContent as ITextEditorProvider;
-			
-			if (provider != null) {
-				XmlView.FormatXml(provider.TextEditor);
+			ITextEditor textEditor = SD.GetActiveViewContentService<ITextEditor>();
+			if (textEditor != null) {
+				XmlView.FormatXml(textEditor);
 			}
 		}
 	}

src/AddIns/DisplayBindings/XmlEditor/Project/Src/RemoveXPathHighlightingCommand.cs

@@ -30,11 +30,7 @@ namespace ICSharpCode.XmlEditor
 		public void RemoveXPathNodeTextMarkers()
 		{
 			foreach (IViewContent view in workbench.ViewContentCollection) {
-				ITextEditorProvider textEditorProvider = view as ITextEditorProvider;
-				if (textEditorProvider != null) {
-					XPathNodeTextMarker marker = new XPathNodeTextMarker(textEditorProvider.TextEditor.Document);
-					marker.RemoveMarkers();
-				}
+				XPathNodeTextMarker.RemoveMarkers(view);
 			}
 		}
 	}

src/AddIns/DisplayBindings/XmlEditor/Project/Src/RunXslTransformCommand.cs

@@ -70,15 +70,7 @@ namespace ICSharpCode.XmlEditor
 		
 		static string GetStylesheetContent(string fileName)
 		{
-			// File already open?
-			ITextEditorProvider view = FileService.GetOpenFile(fileName) as ITextEditorProvider;
-			if (view != null) {
-				return view.TextEditor.Document.Text;
-			}
-			
-			// Read in file contents.
-			StreamReader reader = new StreamReader(fileName, true);
-			return reader.ReadToEnd();
+			return SD.FileService.GetFileContent(fileName).Text;
 		}
 	}
 }

src/AddIns/DisplayBindings/XmlEditor/Project/Src/XPathNodeTextMarker.cs

@@ -45,15 +45,18 @@ namespace ICSharpCode.XmlEditor
 			}
 		}
 		
-		public void RemoveMarkers()
+		/// <summary>
+		/// Removes all markers from the given view content or text editor.
+		/// </summary>
+		public static void RemoveMarkers(IServiceProvider serviceProvider)
 		{
-			ITextMarkerService markerService = document.GetService(typeof(ITextMarkerService)) as ITextMarkerService;
+			ITextMarkerService markerService = serviceProvider.GetService(typeof(ITextMarkerService)) as ITextMarkerService;
 			if (markerService != null) {
 				markerService.RemoveAll(IsXPathNodeTextMarker);
 			}
 		}
 		
-		bool IsXPathNodeTextMarker(ITextMarker marker)
+		static bool IsXPathNodeTextMarker(ITextMarker marker)
 		{
 			return (Type)marker.Tag == typeof(XPathNodeTextMarker);
 		}

src/AddIns/DisplayBindings/XmlEditor/Project/Src/XPathQueryControl.cs

@@ -428,14 +428,14 @@ namespace ICSharpCode.XmlEditor
 				
 				// Clear previous XPath results.
 				ClearResults();
-				XPathNodeTextMarker marker = new XPathNodeTextMarker(xmlView.TextEditor.Document);
-				marker.RemoveMarkers();
+				XPathNodeTextMarker.RemoveMarkers(xmlView.TextEditor.Document);
 				
 				// Run XPath query.
 				XPathQuery query = new XPathQuery(xmlView.TextEditor, GetNamespaces());
 				XPathNodeMatch[] nodes = query.FindNodes(xpathComboBox.Text);
 				if (nodes.Length > 0) {
 					AddXPathResults(nodes);
+					XPathNodeTextMarker marker = new XPathNodeTextMarker(xmlView.TextEditor.Document);
 					marker.AddMarkers(nodes);
 				} else {
 					AddNoXPathResult();

src/AddIns/DisplayBindings/XmlEditor/Project/Src/XmlDisplayBinding.cs

@@ -63,12 +63,9 @@ namespace ICSharpCode.XmlEditor
 		
 		public static bool XmlViewContentActive {
 			get {
-				if (WorkbenchSingleton.Workbench == null) {
-					return false;
-				}
-				ITextEditorProvider view = WorkbenchSingleton.Workbench.ActiveViewContent as ITextEditorProvider;
-				if (view != null) {
-					return IsFileNameHandled(view.TextEditor.FileName);
+				ITextEditor editor = SD.GetActiveViewContentService<ITextEditor>();
+				if (editor != null) {
+					return IsFileNameHandled(editor.FileName);
 				}
 				return false;
 			}

src/AddIns/DisplayBindings/XmlEditor/Project/Src/XmlView.cs

@@ -82,11 +82,12 @@ namespace ICSharpCode.XmlEditor
 		{
 			get {
 				foreach (IViewContent view in File.RegisteredViewContents) {
-					ITextEditorProvider provider = view as ITextEditorProvider;
-					if (provider != null) {
+					IFileDocumentProvider provider = view.GetService<IFileDocumentProvider>();
+					ITextEditor textEditor = view.GetService<ITextEditor>();
+					if (textEditor != null && provider != null) {
 						IDocument document = provider.GetDocumentForFile(File);
 						if (document != null) {
-							return provider.TextEditor;
+							return textEditor;
 						}
 					}
 				}

src/AddIns/DisplayBindings/XmlEditor/Project/Src/XslOutputView.cs

@@ -21,7 +21,7 @@ namespace ICSharpCode.XmlEditor
 			get {
 				if (editor == null) {
 					instance = FileService.NewFile("xslOutput.xml", "");
-					editor = (instance as ITextEditorProvider).TextEditor;
+					editor = instance.GetService<ITextEditor>();
 					instance.Disposed += new EventHandler(InstanceDisposed);
 				}
 				
@@ -33,7 +33,7 @@ namespace ICSharpCode.XmlEditor
 			get {
 				if (instance == null) {
 					instance = FileService.NewFile("xslOutput.xml", "");
-					editor = (instance as ITextEditorProvider).TextEditor;
+					editor = instance.GetService<ITextEditor>();
 					instance.Disposed += new EventHandler(InstanceDisposed);
 				} else {
 					instance.WorkbenchWindow.SelectWindow();

src/AddIns/Misc/SearchAndReplace/Project/Engine/SearchLocation.cs

@@ -8,6 +8,7 @@ using System.Linq;
 
 using ICSharpCode.Core;
 using ICSharpCode.NRefactory.Editor;
+using ICSharpCode.SharpDevelop;
 using ICSharpCode.SharpDevelop.Editor;
 using ICSharpCode.SharpDevelop.Gui;
 using ICSharpCode.SharpDevelop.Project;
@@ -47,16 +48,20 @@ namespace SearchAndReplace
 		{
 			List<FileName> files = new List<FileName>();
 			
+			ITextEditor editor;
 			switch (Target) {
 				case SearchTarget.CurrentDocument:
 				case SearchTarget.CurrentSelection:
-					ITextEditorProvider vc = WorkbenchSingleton.Workbench.ActiveViewContent as ITextEditorProvider;
-					if (vc != null)
-						files.Add(vc.TextEditor.FileName);
+					editor = SD.GetActiveViewContentService<ITextEditor>();
+					if (editor != null)
+						files.Add(editor.FileName);
 					break;
 				case SearchTarget.AllOpenFiles:
-					foreach (ITextEditorProvider editor in WorkbenchSingleton.Workbench.ViewContentCollection.OfType<ITextEditorProvider>())
-						files.Add(editor.TextEditor.FileName);
+					foreach (var vc in WorkbenchSingleton.Workbench.ViewContentCollection) {
+						editor = vc.GetService<ITextEditor>();
+						if (editor != null)
+							files.Add(editor.FileName);
+					}
 					break;
 				case SearchTarget.WholeProject:
 					if (ProjectService.CurrentProject == null)

src/AddIns/Misc/SearchAndReplace/Project/Engine/SearchManager.cs

@@ -420,27 +420,22 @@ namespace SearchAndReplace
 		#region TextEditor helpers
 		static ITextEditor OpenTextArea(string fileName, bool switchToOpenedView = true)
 		{
-			ITextEditorProvider textEditorProvider;
+			IViewContent viewContent;
 			if (fileName != null) {
-				textEditorProvider = FileService.OpenFile(fileName, switchToOpenedView) as ITextEditorProvider;
+				viewContent = FileService.OpenFile(fileName, switchToOpenedView);
 			} else {
-				textEditorProvider = WorkbenchSingleton.Workbench.ActiveViewContent as ITextEditorProvider;
+				viewContent = WorkbenchSingleton.Workbench.ActiveViewContent;
 			}
 
-			if (textEditorProvider != null) {
-				return textEditorProvider.TextEditor;
+			if (viewContent != null) {
+				return viewContent.GetService<ITextEditor>();
 			}
 			return null;
 		}
 		
 		public static ITextEditor GetActiveTextEditor()
 		{
-			ITextEditorProvider provider = SD.Workbench.ActiveViewContent as ITextEditorProvider;
-			if (provider != null) {
-				return provider.TextEditor;
-			} else {
-				return null;
-			}
+			return SD.GetActiveViewContentService<ITextEditor>();
 		}
 		
 		public static ISegment GetActiveSelection(bool useAnchors)

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Document/TextDocument.cs

@@ -118,6 +118,9 @@ namespace ICSharpCode.AvalonEdit.Document
 			if (textSource == null)
 				throw new ArgumentNullException("textSource");
 			
+			if (textSource is ReadOnlyDocument)
+				textSource = textSource.CreateSnapshot(); // retrieve underlying text source, which might be a RopeTextSource
+			
 			RopeTextSource rts = textSource as RopeTextSource;
 			if (rts != null)
 				return rts.GetRope();

src/Main/Base/Project/Src/Bookmarks/Commands/MenuCommands.cs

@@ -14,9 +14,8 @@ namespace ICSharpCode.SharpDevelop.Bookmarks
 	{
 		public override void Run()
 		{
-			ITextEditorProvider provider = WorkbenchSingleton.Workbench.ActiveViewContent as ITextEditorProvider;
-			if (provider != null) {
-				ITextEditor editor = provider.TextEditor;
+			ITextEditor editor = SD.GetActiveViewContentService<ITextEditor>();
+			if (editor != null) {
 				IBookmarkMargin margin = editor.GetService(typeof(IBookmarkMargin)) as IBookmarkMargin;
 				if (editor != null && margin != null) {
 					Run(editor, margin);

src/Main/Base/Project/Src/Commands/CustomStringTagProvider.cs

@@ -84,23 +84,23 @@ namespace ICSharpCode.SharpDevelop.Commands
 					
 				case "CURLINE":
 					{
-						IPositionable positionable = WorkbenchSingleton.Workbench.ActiveViewContent as IPositionable;
+						IPositionable positionable = SD.GetActiveViewContentService<IPositionable>();
 						if (positionable != null)
 							return positionable.Line.ToString();
 						return string.Empty;
 					}
 				case "CURCOL":
 					{
-						IPositionable positionable = WorkbenchSingleton.Workbench.ActiveViewContent as IPositionable;
+						IPositionable positionable = SD.GetActiveViewContentService<IPositionable>();
 						if (positionable != null)
 							return positionable.Column.ToString();
 						return string.Empty;
 					}
 				case "CURTEXT":
 					{
-						var tecp = WorkbenchSingleton.Workbench.ActiveViewContent as ITextEditorProvider;
-						if (tecp != null) {
-							return tecp.TextEditor.SelectedText;
+						ITextEditor editor = SD.GetActiveViewContentService<ITextEditor>();
+						if (editor != null) {
+							return editor.SelectedText;
 						}
 						return string.Empty;
 					}

src/Main/Base/Project/Src/Commands/DebugCommands.cs

@@ -117,23 +117,12 @@ namespace ICSharpCode.SharpDevelop.Project.Commands
 	{
 		public override void Run()
 		{
-			var viewContent = WorkbenchSingleton.Workbench.ActiveContent;
-			ITextEditorProvider provider = viewContent as ITextEditorProvider;
-			ITextEditor editor = null;
+			ITextEditor editor = SD.GetActiveViewContentService<ITextEditor>();
 			
-			if (provider != null) {
-				editor = provider.TextEditor;
+			if (editor != null) {
 				if (!string.IsNullOrEmpty(editor.FileName)) {
 					DebuggerService.ToggleBreakpointAt(editor, editor.Caret.Line, typeof(BreakpointBookmark));
 				}
-			} else {
-				var view = viewContent as AbstractViewContentWithoutFile;
-				if (view != null) {
-					editor = view.GetService(typeof(ITextEditor)) as ITextEditor;
-					if (editor != null) {
-						DebuggerService.ToggleBreakpointAt(editor, editor.Caret.Line, typeof(DecompiledBreakpointBookmark));
-					}
-				}
 			}
 		}
 	}

src/Main/Base/Project/Src/Editor/AvalonEdit/TextContentCondition.cs

@@ -21,12 +21,9 @@ namespace ICSharpCode.SharpDevelop.Editor.AvalonEdit
 		public bool IsValid(object caller, Condition condition)
 		{
 			string textcontent = condition.Properties["textcontent"];
-			IViewContent content = WorkbenchSingleton.Workbench.ActiveViewContent;
-			if (content is ITextEditorProvider) {
-				var ctrl = (content as ITextEditorProvider).TextEditor.GetService(typeof(ICSharpCode.AvalonEdit.TextEditor)) as ICSharpCode.AvalonEdit.TextEditor;
-				if (ctrl != null && ctrl.SyntaxHighlighting != null) {
-					return string.Equals(textcontent, ctrl.SyntaxHighlighting.Name, StringComparison.OrdinalIgnoreCase);
-				}
+			var editor = SD.GetActiveViewContentService<ICSharpCode.AvalonEdit.TextEditor>();
+			if (editor != null) {
+				return string.Equals(textcontent, editor.SyntaxHighlighting.Name, StringComparison.OrdinalIgnoreCase);
 			}
 			return false;
 		}

src/Main/Base/Project/Src/Editor/AvalonEdit/TextSelectedCondition.cs

@@ -11,9 +11,8 @@ namespace ICSharpCode.SharpDevelop.Editor.AvalonEdit
 	{
 		public bool IsValid(object owner, Condition condition)
 		{
-			ITextEditorProvider textEditorProvider = WorkbenchSingleton.Workbench.ActiveViewContent as ITextEditorProvider;
-			if (textEditorProvider != null) {
-				ITextEditor textEditor = textEditorProvider.TextEditor;
+			ITextEditor textEditor = SD.GetActiveViewContentService<ITextEditor>();
+			if (textEditor != null) {
 				return textEditor.SelectionLength > 0;
 			}
 			return false;

src/Main/Base/Project/Src/Editor/Commands/CommentRegion.cs

@@ -9,7 +9,7 @@ using ICSharpCode.SharpDevelop;
 namespace ICSharpCode.SharpDevelop.Editor.Commands
 {
 	/// <summary>
-	/// Description of CommentRegion
+	/// Surrounds the selected text in a comment
 	/// </summary>
 	public class CommentRegion : AbstractMenuCommand
 	{
@@ -18,13 +18,12 @@ namespace ICSharpCode.SharpDevelop.Editor.Commands
 		/// </summary>
 		public override void Run()
 		{
-			ITextEditorProvider provider = WorkbenchSingleton.Workbench.ActiveViewContent as ITextEditorProvider;
-			
-			if (provider == null)
+			ITextEditor editor = SD.GetActiveViewContentService<ITextEditor>();
+			if (editor == null)
 				return;
 			
-			using (provider.TextEditor.Document.OpenUndoGroup())
-				provider.TextEditor.Language.FormattingStrategy.SurroundSelectionWithComment(provider.TextEditor);
+			using (editor.Document.OpenUndoGroup())
+				editor.Language.FormattingStrategy.SurroundSelectionWithComment(editor);
 		}
 	}
 }

src/Main/Base/Project/Src/Editor/Commands/GoToMatchingBrace.cs

@@ -11,9 +11,9 @@ namespace ICSharpCode.SharpDevelop.Editor.Commands
 	{
 		public override void Run()
 		{
-			ITextEditorProvider editorProvider = WorkbenchSingleton.Workbench.ActiveViewContent as ITextEditorProvider;
-			if (editorProvider != null) {
-				Run(editorProvider.TextEditor, editorProvider.TextEditor.Caret.Offset);
+			ITextEditor editor = SD.GetActiveViewContentService<ITextEditor>();
+			if (editor != null) {
+				Run(editor, editor.Caret.Offset);
 			}
 		}
 		

src/Main/Base/Project/Src/Editor/Commands/IndentSelection.cs

@@ -20,21 +20,20 @@ namespace ICSharpCode.SharpDevelop.Editor.Commands
 		/// </summary>
 		public override void Run()
 		{
-			ITextEditorProvider provider = WorkbenchSingleton.Workbench.ActiveViewContent as ITextEditorProvider;
-			
-			if (provider == null)
+			ITextEditor editor = SD.GetActiveViewContentService<ITextEditor>();
+			if (editor == null)
 				return;
 			
 			int beginLine = 1;
-			int endLine = provider.TextEditor.Document.LineCount;
+			int endLine = editor.Document.LineCount;
 			
-			if (provider.TextEditor.SelectionLength != 0) {
-				beginLine = provider.TextEditor.Document.GetLineByOffset(provider.TextEditor.SelectionStart).LineNumber;
-				endLine = provider.TextEditor.Document.GetLineByOffset(provider.TextEditor.SelectionStart + provider.TextEditor.SelectionLength).LineNumber;
+			if (editor.SelectionLength != 0) {
+				beginLine = editor.Document.GetLineByOffset(editor.SelectionStart).LineNumber;
+				endLine = editor.Document.GetLineByOffset(editor.SelectionStart + editor.SelectionLength).LineNumber;
 			}
 			
-			using (provider.TextEditor.Document.OpenUndoGroup())
-				provider.TextEditor.Language.FormattingStrategy.IndentLines(provider.TextEditor, beginLine, endLine);
+			using (editor.Document.OpenUndoGroup())
+				editor.Language.FormattingStrategy.IndentLines(editor, beginLine, endLine);
 		}
 	}
 }

src/Main/Base/Project/Src/Editor/Commands/InsertGuidCommand.cs

@@ -11,12 +11,7 @@ namespace ICSharpCode.SharpDevelop.Editor.Commands
 	{
 		public override void Run()
 		{
-			IViewContent viewContent = WorkbenchSingleton.Workbench.ActiveViewContent;
-			if (viewContent == null || !(viewContent is ITextEditorProvider)) {
-				return;
-			}
-			
-			ITextEditor textEditor = ((ITextEditorProvider)viewContent).TextEditor;
+			ITextEditor textEditor = SD.GetActiveViewContentService<ITextEditor>();
 			if (textEditor == null) {
 				return;
 			}

src/Main/Base/Project/Src/Editor/Commands/PasteAsCommands.cs

@@ -14,19 +14,13 @@ namespace ICSharpCode.SharpDevelop.Editor.Commands
 	{
 		public override void Run()
 		{
-			string clipboardText = ClipboardWrapper.GetText();
-			if (string.IsNullOrEmpty(clipboardText))
-				return;
-			
-			IViewContent viewContent = WorkbenchSingleton.Workbench.ActiveViewContent;
-			if (viewContent == null || !(viewContent is ITextEditorProvider)) {
+			ITextEditor textEditor = SD.GetActiveViewContentService<ITextEditor>();
+			if (textEditor == null)
 				return;
-			}
 			
-			ITextEditor textEditor = ((ITextEditorProvider)viewContent).TextEditor;
-			if (textEditor == null) {
+			string clipboardText = ClipboardWrapper.GetText();
+			if (string.IsNullOrEmpty(clipboardText))
 				return;
-			}
 			
 			using (textEditor.Document.OpenUndoGroup())
 				Run(textEditor, clipboardText);

src/Main/Base/Project/Src/Editor/Commands/ShowColorDialog.cs

@@ -13,12 +13,9 @@ namespace ICSharpCode.SharpDevelop.Editor.Commands
 	{
 		public override void Run()
 		{
-			IViewContent viewContent = WorkbenchSingleton.Workbench.ActiveViewContent;
-			
-			if (viewContent == null || !(viewContent is ITextEditorProvider)) {
+			ITextEditor textEditor = SD.GetActiveViewContentService<ITextEditor>();
+			if (textEditor == null)
 				return;
-			}
-			ITextEditor textEditor = ((ITextEditorProvider)viewContent).TextEditor;
 			
 			using (SharpDevelopColorDialog cd = new SharpDevelopColorDialog()) {
 				if (cd.ShowDialog(ICSharpCode.SharpDevelop.Gui.WorkbenchSingleton.MainWin32Window) == DialogResult.OK) {

src/Main/Base/Project/Src/Editor/Commands/SymbolUnderCaretMenuCommand.cs

@@ -18,9 +18,9 @@ namespace ICSharpCode.SharpDevelop.Editor.Commands
 	{
 		public override void Run()
 		{
-			ITextEditorProvider editorProvider = WorkbenchSingleton.Workbench.ActiveViewContent as ITextEditorProvider;
-			if (editorProvider != null) {
-				Run(editorProvider.TextEditor, editorProvider.TextEditor.Caret.Offset);
+			ITextEditor editor = SD.GetActiveViewContentService<ITextEditor>();
+			if (editor != null) {
+				Run(editor, editor.Caret.Offset);
 			}
 		}
 		

src/Main/Base/Project/Src/Editor/IFileDocumentProvider.cs

@@ -10,6 +10,7 @@ namespace ICSharpCode.SharpDevelop.Editor
 	/// Interface for view contents that provide a text editor document
 	/// for one or more <see cref="OpenedFile"/>s.
 	/// </summary>
+	[ViewContentService]
 	public interface IFileDocumentProvider
 	{
 		/// <summary>

src/Main/Base/Project/Src/Editor/ITextEditor.cs

@@ -13,8 +13,10 @@ using ICSharpCode.SharpDevelop.Refactoring;
 
 namespace ICSharpCode.SharpDevelop.Editor
 {
+	[ViewContentService]
 	public interface ITextEditorProvider : IFileDocumentProvider
 	{
+		[Obsolete("Use viewContent.GetService<ITextEditor>() instead.")]
 		ITextEditor TextEditor {
 			get;
 		}
@@ -23,6 +25,7 @@ namespace ICSharpCode.SharpDevelop.Editor
 	/// <summary>
 	/// Interface for text editors.
 	/// </summary>
+	[ViewContentService]
 	public interface ITextEditor : IServiceProvider
 	{
 		/// <summary>

src/Main/Base/Project/Src/Gui/ContentInterfaces/IEditable.cs

@@ -7,6 +7,7 @@ using System;
 
 namespace ICSharpCode.SharpDevelop.Gui
 {
+	[ViewContentService]
 	public interface IEditable
 	{
 		/// <summary>

src/Main/Base/Project/Src/Gui/ContentInterfaces/IPositionable.cs

@@ -8,6 +8,7 @@ namespace ICSharpCode.SharpDevelop.Gui
 	/// that it's a texteditor which could set the caret to a position inside
 	/// a file.
 	/// </summary>
+	[ViewContentService]
 	public interface IPositionable
 	{
 		/// <summary>

src/Main/Base/Project/Src/Gui/Dialogs/GotoDialog.cs

@@ -336,11 +336,7 @@ namespace ICSharpCode.SharpDevelop.Gui
 		
 		ITextEditor GetEditor()
 		{
-			IViewContent viewContent = WorkbenchSingleton.Workbench.ActiveViewContent;
-			if (viewContent is ITextEditorProvider) {
-				return ((ITextEditorProvider)viewContent).TextEditor;
-			}
-			return null;
+			return SD.GetActiveViewContentService<ITextEditor>();
 		}
 		
 		void okButtonClick(object sender, RoutedEventArgs e)

src/Main/Base/Project/Src/Gui/Dialogs/ReferenceDialog/ServiceReference/ActiveTextEditors.cs

@@ -2,6 +2,7 @@
 // This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
 
 using System;
+using ICSharpCode.Core;
 using ICSharpCode.SharpDevelop.Editor;
 
 namespace ICSharpCode.SharpDevelop.Gui.Dialogs.ReferenceDialog.ServiceReference	
@@ -20,9 +21,8 @@ namespace ICSharpCode.SharpDevelop.Gui.Dialogs.ReferenceDialog.ServiceReference
 		ITextEditor GetTextEditor(string fileName)
 		{
 			IViewContent viewContent = FileService.GetOpenFile(fileName);
-			var textEditorProvider = viewContent as ITextEditorProvider;
-			if (textEditorProvider != null) {
-				return textEditorProvider.TextEditor;
+			if (viewContent != null) {
+				return viewContent.GetService<ITextEditor>();
 			}
 			return null;
 		}

src/Main/Base/Project/Src/Gui/Dialogs/WordCountDialog.cs

@@ -95,7 +95,7 @@ namespace ICSharpCode.SharpDevelop.Gui
 					case 0: {// current file
 						IViewContent viewContent = WorkbenchSingleton.Workbench.ActiveViewContent;
 						if (viewContent != null) {
-							IEditable editable = viewContent as IEditable;
+							IEditable editable = viewContent.GetService<IEditable>();
 							if (editable == null) {
 								MessageService.ShowWarning("${res:Dialog.WordCountDialog.IsNotTextFile}");
 							} else {
@@ -109,7 +109,7 @@ namespace ICSharpCode.SharpDevelop.Gui
 						if (WorkbenchSingleton.Workbench.ViewContentCollection.Count > 0) {
 							total = new Report(StringParser.Parse("${res:Dialog.WordCountDialog.TotalText}"), 0, 0, 0);
 							foreach (IViewContent content in WorkbenchSingleton.Workbench.ViewContentCollection) {
-								IEditable editable = content as IEditable;
+								IEditable editable = content.GetService<IEditable>();
 								if (editable != null) {
 									Report r = GetReport(content, editable.CreateSnapshot().CreateReader());
 									if (r != null) {

src/Main/Base/Project/Src/Gui/Pads/DefinitionViewPad.cs

@@ -87,14 +87,19 @@ namespace ICSharpCode.SharpDevelop.Gui
 		Task<ResolveResult> ResolveAtCaretAsync(ParserUpdateStepEventArgs e)
 		{
 			IWorkbenchWindow window = WorkbenchSingleton.Workbench.ActiveWorkbenchWindow;
-			if (window == null) return Task.FromResult<ResolveResult>(null);
-			ITextEditorProvider provider = window.ActiveViewContent as ITextEditorProvider;
-			if (provider == null) return Task.FromResult<ResolveResult>(null);
-			ITextEditor editor = provider.TextEditor;
+			if (window == null) 
+				return Task.FromResult<ResolveResult>(null);
+			IViewContent viewContent = window.ActiveViewContent;
+			if (viewContent == null) 
+				return Task.FromResult<ResolveResult>(null);
+			ITextEditor editor = viewContent.GetService<ITextEditor>();
+			if (editor == null)
+				return Task.FromResult<ResolveResult>(null);
 			
 			// e might be null when this is a manually triggered update
 			// don't resolve when an unrelated file was changed
-			if (e != null && editor.FileName != e.FileName) return null;
+			if (e != null && editor.FileName != e.FileName)
+				return Task.FromResult<ResolveResult>(null);
 			
 			return SD.ParserService.ResolveAsync(editor.FileName, editor.Caret.Location, editor.Document);
 		}
@@ -121,19 +126,8 @@ namespace ICSharpCode.SharpDevelop.Gui
 		/// </summary>
 		void LoadFile(string fileName)
 		{
-			// Get currently open text editor that matches the filename.
-			ITextEditor openTextEditor = null;
-			ITextEditorProvider provider = FileService.GetOpenFile(fileName) as ITextEditorProvider;
-			if (provider != null) {
-				openTextEditor = provider.TextEditor;
-			}
-			
 			// Load the text into the definition view's text editor.
-			if (openTextEditor != null) {
-				ctl.Text = openTextEditor.Document.Text;
-			} else {
-				ctl.Load(fileName);
-			}
+			ctl.Document = new TextDocument(SD.FileService.GetFileContent(fileName));
 			currentFileName = fileName;
 			ctl.SyntaxHighlighting = HighlightingManager.Instance.GetDefinitionByExtension(Path.GetExtension(fileName));
 		}

src/Main/Base/Project/Src/Gui/Pads/TaskList/TaskListPad.cs

@@ -95,12 +95,12 @@ namespace ICSharpCode.SharpDevelop.Gui
 			if (isInitialized)
 				UpdateItems();
 			
-			ITextEditorProvider provider = WorkbenchSingleton.Workbench.ActiveViewContent as ITextEditorProvider;
+			ITextEditor editor = SD.GetActiveViewContentService<ITextEditor>();
 			
-			if (provider != null) {
+			if (editor != null) {
 				// ensure we don't attach multiple times to the same editor
-				provider.TextEditor.Caret.LocationChanged -= CaretPositionChanged;
-				provider.TextEditor.Caret.LocationChanged += CaretPositionChanged;
+				editor.Caret.LocationChanged -= CaretPositionChanged;
+				editor.Caret.LocationChanged += CaretPositionChanged;
 			}
 		}
 
@@ -199,7 +199,7 @@ namespace ICSharpCode.SharpDevelop.Gui
 					return ProjectService.CurrentProject != null && ProjectService.CurrentProject.FindFile(item.FileName) != null;
 				case 2:
 					// All open documents
-					return WorkbenchSingleton.Workbench.ViewContentCollection.OfType<ITextEditorProvider>().Any(provider => item.FileName == provider.TextEditor.FileName);
+					return WorkbenchSingleton.Workbench.ViewContentCollection.Select(vc => vc.GetService<ITextEditor>()).Any(editor => editor != null && item.FileName == editor.FileName);
 				case 3:
 					// Document
 					return WorkbenchSingleton.Workbench.ActiveViewContent != null && WorkbenchSingleton.Workbench.ActiveViewContent.PrimaryFileName == item.FileName;
@@ -221,7 +221,7 @@ namespace ICSharpCode.SharpDevelop.Gui
 			
 			IUnresolvedFile parseInfo = SD.ParserService.GetExistingUnresolvedFile(WorkbenchSingleton.Workbench.ActiveViewContent.PrimaryFileName);
 			if (parseInfo != null) {
-				IPositionable positionable = WorkbenchSingleton.Workbench.ActiveViewContent as IPositionable;
+				IPositionable positionable = WorkbenchSingleton.Workbench.ActiveViewContent.GetService<IPositionable>();
 				if (positionable != null) {
 					var c = parseInfo.GetInnermostTypeDefinition(positionable.Line, positionable.Column);
 					if (c != null) return c;

src/Main/Base/Project/Src/Gui/Pads/ToolsPad.cs

@@ -10,6 +10,7 @@ namespace ICSharpCode.SharpDevelop.Gui
 	/// <summary>
 	/// Implement this interface to make your view content display tools in the tool box.
 	/// </summary>
+	[ViewContentService]
 	public interface IToolsHost
 	{
 		/// <summary>
@@ -39,7 +40,7 @@ namespace ICSharpCode.SharpDevelop.Gui
 		
 		void WorkbenchActiveContentChanged(object sender, EventArgs e)
 		{
-			IToolsHost th = WorkbenchSingleton.Workbench.ActiveViewContent as IToolsHost;
+			IToolsHost th = SD.GetActiveViewContentService<IToolsHost>();
 			if (th != null && th.ToolsContent != null) {
 				contentControl.SetContent(th.ToolsContent, th);
 			} else {

src/Main/Base/Project/Src/Services/Debugger/CurrentLineBookmark.cs

@@ -24,9 +24,11 @@ namespace ICSharpCode.SharpDevelop.Debugging
 		
 		public static void SetPosition(IViewContent viewContent, int markerStartLine, int markerStartColumn, int markerEndLine, int markerEndColumn)
 		{
-			ITextEditorProvider tecp = viewContent as ITextEditorProvider;
-			if (tecp != null) {
-				SetPosition(tecp.TextEditor.FileName, tecp.TextEditor.Document, markerStartLine, markerStartColumn, markerEndLine, markerEndColumn);
+			if (viewContent == null)
+				return;
+			ITextEditor editor = viewContent.GetService<ITextEditor>();
+			if (editor != null) {
+				SetPosition(editor.FileName, editor.Document, markerStartLine, markerStartColumn, markerEndLine, markerEndColumn);
 			}
 		}
 		

src/Main/Base/Project/Src/Services/Debugger/DebuggerService.cs

@@ -289,8 +289,12 @@ namespace ICSharpCode.SharpDevelop.Debugging
 		public static void JumpToCurrentLine(string sourceFullFilename, int startLine, int startColumn, int endLine, int endColumn)
 		{
 			IViewContent viewContent = FileService.OpenFile(sourceFullFilename);
-			if (viewContent is ITextEditorProvider)
-				((ITextEditorProvider)viewContent).TextEditor.JumpTo(startLine, startColumn);
+			if (viewContent != null) {
+				IPositionable positionable = viewContent.GetService<IPositionable>();
+				if (positionable != null) {
+					positionable.JumpTo(startLine, startColumn);
+				}
+			}
 			CurrentLineBookmark.SetPosition(viewContent, startLine, startColumn, endLine, endColumn);
 		}
 	}

src/Main/Base/Project/Src/Services/File/IFileService.cs

@@ -44,6 +44,7 @@ namespace ICSharpCode.SharpDevelop
 		/// <remarks>
 		/// This method is thread-safe. This method involves waiting for the main thread, so using it while
 		/// holding a lock can lead to deadlocks.
+		/// This method never returns null.
 		/// </remarks>
 		ITextSource GetFileContent(FileName fileName);
 		
@@ -65,6 +66,7 @@ namespace ICSharpCode.SharpDevelop
 		/// </summary>
 		/// <remarks>
 		/// This method is thread-safe.
+		/// This method never returns null.
 		/// </remarks>
 		ITextSource GetFileContentFromDisk(FileName fileName, CancellationToken cancellationToken = default(CancellationToken));
 		#endregion

src/Main/Base/Project/Src/Services/File/OpenedFile.cs

@@ -348,7 +348,7 @@ namespace ICSharpCode.SharpDevelop
 		
 		static Properties GetMemento(IViewContent viewContent)
 		{
-			IMementoCapable mementoCapable = viewContent as IMementoCapable;
+			IMementoCapable mementoCapable = viewContent.GetService<IMementoCapable>();
 			if (mementoCapable == null) {
 				return null;
 			} else {

src/Main/Base/Project/Src/Services/SD.cs

@@ -58,6 +58,33 @@ namespace ICSharpCode.SharpDevelop
 			return ServiceSingleton.ServiceProvider.GetRequiredService<T>();
 		}
 		
+		/// <summary>
+		/// Equivalent to <code>SD.Workbench.ActiveViewContent.GetService&lt;T&gt;()</code>,
+		/// but does not throw a NullReferenceException when ActiveViewContent is null.
+		/// (instead, null is returned).
+		/// </summary>
+		public static T GetActiveViewContentService<T>() where T : class
+		{
+			return (T)GetActiveViewContentService(typeof(T));
+		}
+		
+		/// <summary>
+		/// Equivalent to <code>SD.Workbench.ActiveViewContent.GetService(type)</code>,
+		/// but does not throw a NullReferenceException when ActiveViewContent is null.
+		/// (instead, null is returned).
+		/// </summary>
+		public static object GetActiveViewContentService(Type type)
+		{
+			var workbench = ServiceSingleton.ServiceProvider.GetService(typeof(IWorkbench)) as IWorkbench;
+			if (workbench != null) {
+				var activeViewContent = workbench.ActiveViewContent;
+				if (activeViewContent != null) {
+					return activeViewContent.GetService(type);
+				}
+			}
+			return null;
+		}
+		
 		/// <summary>
 		/// Gets the workbench.
 		/// </summary>

src/Main/Core/Project/Src/Services/PropertyService/Properties.cs

@@ -21,6 +21,9 @@ namespace ICSharpCode.Core
 	/// and set from a object from the same class.
 	/// This is used to save and restore the state of GUI objects.
 	/// </summary>
+	/// <remarks>
+	/// This interface is used as a [ViewContentService]
+	/// </remarks>
 	public interface IMementoCapable
 	{
 		/// <summary>

src/Main/SharpDevelop/Sda/Document.cs

@@ -15,9 +15,11 @@ namespace ICSharpCode.SharpDevelop.Sda
 	{
 		internal static Document FromWindow(IViewContent viewContent)
 		{
-			ITextEditorProvider editable = viewContent as ITextEditorProvider;
-			if (editable != null) {
-				return new Document(viewContent, editable.TextEditor.PrimaryView.Document);
+			if (viewContent == null)
+				return null;
+			ITextEditor editor = viewContent.GetService(typeof(ITextEditor)) as ITextEditor;
+			if (editor != null) {
+				return new Document(viewContent, editor.Document);
 			} else {
 				return null;
 			}

src/Main/SharpDevelop/Workbench/WpfWorkbench.cs

@@ -493,7 +493,7 @@ namespace ICSharpCode.SharpDevelop.Workbench
 		/// </summary>
 		public void StoreMemento(IViewContent viewContent)
 		{
-			IMementoCapable mementoCapable = viewContent as IMementoCapable;
+			IMementoCapable mementoCapable = viewContent.GetService<IMementoCapable>();
 			if (mementoCapable != null && LoadDocumentProperties) {
 				if (viewContent.PrimaryFileName == null)
 					return;
@@ -510,7 +510,7 @@ namespace ICSharpCode.SharpDevelop.Workbench
 		
 		void LoadViewContentMemento(IViewContent viewContent)
 		{
-			IMementoCapable mementoCapable = viewContent as IMementoCapable;
+			IMementoCapable mementoCapable = viewContent.GetService<IMementoCapable>();
 			if (mementoCapable != null && LoadDocumentProperties) {
 				if (viewContent.PrimaryFileName == null)
 					return;