Address basic review feedback.

src/EditorFeatures/CSharp/CommentSelection/ToggleBlockCommentCommandHandler.cs

@@ -6,6 +6,7 @@
 using System.ComponentModel.Composition;
 using System.Linq;
 using System.Threading;
+using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.CommentSelection;
 using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.Editor.Implementation.CommentSelection;
@@ -27,17 +28,19 @@ namespace Microsoft.CodeAnalysis.Editor.CSharp.CommentSelection
 {
     /* TODO - Modify these once the toggle block comment handler is added.
     [Export(typeof(VSCommanding.ICommandHandler))]
-    [ContentType(ContentTypeNames.RoslynContentType)]
+    [ContentType(ContentTypeNames.CSharpContentType)]
     [Name(PredefinedCommandHandlerNames.CommentSelection)]*/
     internal class ToggleBlockCommentCommandHandler :
-        AbstractCommentSelectionCommandHandler/*,
+        AbstractCommentSelectionBase/*,
         VSCommanding.ICommandHandler<CommentSelectionCommandArgs>*/
     {
         [ImportingConstructor]
         internal ToggleBlockCommentCommandHandler(
             ITextUndoHistoryRegistry undoHistoryRegistry,
-            IEditorOperationsFactoryService editorOperationsFactoryService) : base(undoHistoryRegistry, editorOperationsFactoryService)
-        { }
+            IEditorOperationsFactoryService editorOperationsFactoryService)
+            : base(undoHistoryRegistry, editorOperationsFactoryService)
+        {
+        }
 
         /* TODO - modify once the toggle block comment handler is added.
         public VSCommanding.CommandState GetCommandState(CommentSelectionCommandArgs args)
@@ -47,93 +50,89 @@ public VSCommanding.CommandState GetCommandState(CommentSelectionCommandArgs arg
 
         public bool ExecuteCommand(CommentSelectionCommandArgs args, CommandExecutionContext context)
         {
-            return ExecuteCommand(args.TextView, args.SubjectBuffer, Operation.Toggle, context);
+            return ExecuteCommand(args.TextView, args.SubjectBuffer, Operation.Undefined, context);
         }*/
 
         public override string DisplayName => EditorFeaturesResources.Toggle_Block_Comment;
 
-        protected override string GetTitle(Operation operation)
-        {
-            return EditorFeaturesResources.Toggle_Block_Comment;
-        }
-
-        protected override string GetMessage(Operation operation)
-        {
-            return EditorFeaturesResources.Toggling_block_comment_on_selection;
-        }
+        protected override string GetTitle(Operation operation) => EditorFeaturesResources.Toggle_Block_Comment;
 
-        protected override void SetTrackingSpans(ITextView textView, ITextBuffer buffer, List<CommentTrackingSpan> trackingSpans)
-        {
-            var spans = trackingSpans.Select(trackingSpan => trackingSpan.ToSelection(buffer));
-            textView.GetMultiSelectionBroker().SetSelectionRange(spans, spans.Last());
-        }
+        protected override string GetMessage(Operation operation) => EditorFeaturesResources.Toggling_block_comment;
 
-        internal override void CollectEdits(Document document, ICommentSelectionService service, NormalizedSnapshotSpanCollection selectedSpans,
-            List<TextChange> textChanges, List<CommentTrackingSpan> trackingSpans, Operation operation, CancellationToken cancellationToken)
+        internal async override Task<CommentSelectionResult> CollectEdits(Document document, ICommentSelectionService service,
+            NormalizedSnapshotSpanCollection selectedSpans, Operation operation, CancellationToken cancellationToken)
         {
+            var emptyResult = new CommentSelectionResult(new List<TextChange>(), new List<CommentTrackingSpan>(), operation);
             var experimentationService = document.Project.Solution.Workspace.Services.GetRequiredService<IExperimentationService>();
             if (!experimentationService.IsExperimentEnabled(WellKnownExperimentNames.RoslynToggleBlockComment))
             {
-                return;
+                return emptyResult;
             }
 
-            if (selectedSpans.IsEmpty())
-            {
-                return;
-            }
+            var root = document.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
+            var commentInfo = await service.GetInfoAsync(document, selectedSpans.First().Span.ToTextSpan(), cancellationToken).ConfigureAwait(false);
 
-            var getRoot = document.GetSyntaxRootAsync();
-            var commentInfo = service.GetInfoAsync(document, selectedSpans.First().Span.ToTextSpan(), cancellationToken).WaitAndGetResult(cancellationToken);
-            var root = getRoot.WaitAndGetResult(cancellationToken);
             if (commentInfo.SupportsBlockComment)
             {
-                ToggleBlockComments(commentInfo, root, selectedSpans, textChanges, trackingSpans);
+                return ToggleBlockComments(commentInfo, await root, selectedSpans);
             }
+
+            return emptyResult;
         }
 
-        private static void ToggleBlockComments(CommentSelectionInfo commentInfo, SyntaxNode root, NormalizedSnapshotSpanCollection selectedSpans,
-            List<TextChange> textChanges, List<CommentTrackingSpan> trackingSpans)
+
+        private static CommentSelectionResult ToggleBlockComments(CommentSelectionInfo commentInfo, SyntaxNode root,
+            NormalizedSnapshotSpanCollection selectedSpans)
         {
             var blockCommentedSpans = GetDescendentBlockCommentSpansFromRoot(root);
-            var blockCommentSelectionHelpers = selectedSpans.Select(span => new BlockCommentSelectionHelper(blockCommentedSpans, span));
-
-            // If there is a multi selection, either uncomment all or comment all.
-            var onlyAddComment = false;
-            if (selectedSpans.Count > 1)
-            {
-                onlyAddComment = blockCommentSelectionHelpers.Where(helper => !helper.IsEntirelyCommented()).Any();
-            }
-
+            var blockCommentSelectionHelpers = selectedSpans
+                .Select(span => new BlockCommentSelectionHelper(blockCommentedSpans, span))
+                .ToList();
+
+            var returnOperation = Operation.Uncomment;
+            var uncommentChanges = new List<TextChange>();
+            var uncommentTrackingSpans = new List<CommentTrackingSpan>();
+            // Try to uncomment until an uncommented span is found.
             foreach (var blockCommentSelection in blockCommentSelectionHelpers)
             {
-                if (!onlyAddComment && TryUncommentBlockComment(blockCommentedSpans, blockCommentSelection, textChanges, trackingSpans, commentInfo))
-                { }
-                else
+                var hasCommentsToRemove = TryUncommentBlockComment(
+                    blockCommentedSpans, blockCommentSelection, uncommentChanges, uncommentTrackingSpans, commentInfo);
+                // If any selection does not have comments to remove, then the operation should be comment.
+                if (!hasCommentsToRemove)
                 {
-                    BlockCommentSpan(blockCommentSelection, textChanges, trackingSpans, root, commentInfo);
+                    returnOperation = Operation.Comment;
+                    break;
                 }
             }
+
+            if (returnOperation == Operation.Comment)
+            {
+                var commentChanges = new List<TextChange>();
+                var commentTrackingSpans = new List<CommentTrackingSpan>();
+                blockCommentSelectionHelpers.ForEach(
+                    blockCommentSelection => BlockCommentSpan(blockCommentSelection, root, commentChanges, commentTrackingSpans, commentInfo));
+                return new CommentSelectionResult(commentChanges, commentTrackingSpans, returnOperation);
+            }
+            else
+            {
+                return new CommentSelectionResult(uncommentChanges, uncommentTrackingSpans, returnOperation);
+            }
         }
 
-        private static bool TryUncommentBlockComment(IEnumerable<Span> blockCommentedSpans, BlockCommentSelectionHelper blockCommentSelectionHelper,
-            List<TextChange> textChanges, List<CommentTrackingSpan> trackingSpans, CommentSelectionInfo commentInfo)
+        private static bool TryUncommentBlockComment(IEnumerable<Span> blockCommentedSpans,
+            BlockCommentSelectionHelper blockCommentSelectionHelper, List<TextChange> textChanges,
+            List<CommentTrackingSpan> trackingSpans, CommentSelectionInfo commentInfo)
         {
             // If the selection is just a caret, try and uncomment blocks on the same line with only whitespace on the line.
-            if (blockCommentSelectionHelper.SelectedSpan.IsEmpty && blockCommentSelectionHelper.TryGetBlockCommentOnSameLine(blockCommentedSpans, out var blockCommentOnSameLine))
+            if (blockCommentSelectionHelper.SelectedSpan.IsEmpty
+                && blockCommentSelectionHelper.TryGetBlockCommentOnSameLine(blockCommentedSpans, out var blockCommentOnSameLine))
             {
                 DeleteBlockComment(blockCommentSelectionHelper, blockCommentOnSameLine, textChanges, commentInfo);
-                trackingSpans.Add(blockCommentSelectionHelper.GetTrackingSpan(blockCommentOnSameLine, SpanTrackingMode.EdgeExclusive, Operation.Uncomment));
+                trackingSpans.Add(blockCommentSelectionHelper.GetTrackingSpan(blockCommentOnSameLine, SpanTrackingMode.EdgeExclusive));
                 return true;
             }
-
-            // If there are not any block comments intersecting the selection, there is nothing to uncomment.
-            if (!blockCommentSelectionHelper.HasIntersectingBlockComments())
-            {
-                return false;
-            }
-
             // If the selection is entirely commented, remove any block comments that intersect.
-            if (blockCommentSelectionHelper.IsEntirelyCommented())
+            else if (blockCommentSelectionHelper.IsEntirelyCommented())
             {
                 var intersectingBlockComments = blockCommentSelectionHelper.IntersectingBlockComments;
                 foreach (var spanToRemove in intersectingBlockComments)
@@ -141,15 +140,17 @@ protected override void SetTrackingSpans(ITextView textView, ITextBuffer buffer,
                     DeleteBlockComment(blockCommentSelectionHelper, spanToRemove, textChanges, commentInfo);
                 }
                 var trackingSpan = Span.FromBounds(intersectingBlockComments.First().Start, intersectingBlockComments.Last().End);
-                trackingSpans.Add(blockCommentSelectionHelper.GetTrackingSpan(trackingSpan, SpanTrackingMode.EdgeExclusive, Operation.Uncomment));
+                trackingSpans.Add(blockCommentSelectionHelper.GetTrackingSpan(trackingSpan, SpanTrackingMode.EdgeExclusive));
                 return true;
             }
-
-            return false;
+            else
+            {
+                return false;
+            }
         }
 
-        private static void BlockCommentSpan(BlockCommentSelectionHelper blockCommentSelectionHelper, List<TextChange> textChanges,
-            List<CommentTrackingSpan> trackingSpans, SyntaxNode root, CommentSelectionInfo commentInfo)
+        private static void BlockCommentSpan(BlockCommentSelectionHelper blockCommentSelectionHelper, SyntaxNode root,
+            List<TextChange> textChanges, List<CommentTrackingSpan> trackingSpans, CommentSelectionInfo commentInfo)
         {
             if (blockCommentSelectionHelper.HasIntersectingBlockComments())
             {
@@ -165,8 +166,8 @@ protected override void SetTrackingSpans(ITextView textView, ITextBuffer buffer,
                     spanToAdd = Span.FromBounds(caretLocation, caretLocation);
                 }
 
+                trackingSpans.Add(blockCommentSelectionHelper.GetTrackingSpan(spanToAdd, SpanTrackingMode.EdgeInclusive));
                 AddBlockComment(commentInfo, spanToAdd, textChanges);
-                trackingSpans.Add(blockCommentSelectionHelper.GetTrackingSpan(spanToAdd, SpanTrackingMode.EdgeInclusive, Operation.Comment));
             }
         }
 
@@ -174,8 +175,8 @@ protected override void SetTrackingSpans(ITextView textView, ITextBuffer buffer,
         /// Adds a block comment when the selection already contains block comment(s).
         /// The result will be sequential block comments with the entire selection being commented out.
         /// </summary>
-        private static void AddBlockCommentWithIntersectingSpans(BlockCommentSelectionHelper blockCommentSelectionHelper, List<TextChange> textChanges,
-            List<CommentTrackingSpan> trackingSpans, CommentSelectionInfo commentInfo)
+        private static void AddBlockCommentWithIntersectingSpans(BlockCommentSelectionHelper blockCommentSelectionHelper,
+            List<TextChange> textChanges, List<CommentTrackingSpan> trackingSpans, CommentSelectionInfo commentInfo)
         {
             var selectedSpan = blockCommentSelectionHelper.SelectedSpan;
             var spanTrackingMode = SpanTrackingMode.EdgeInclusive;
@@ -190,7 +191,8 @@ protected override void SetTrackingSpans(ITextView textView, ITextBuffer buffer,
             }
 
             // If the start is commented (and not a comment marker), close the current comment and open a new one.
-            if (blockCommentSelectionHelper.IsLocationCommented(selectedSpan.Start) && !blockCommentSelectionHelper.DoesBeginWithBlockComment(commentInfo))
+            if (blockCommentSelectionHelper.IsLocationCommented(selectedSpan.Start)
+                && !blockCommentSelectionHelper.DoesBeginWithBlockComment(commentInfo))
             {
                 InsertText(textChanges, selectedSpan.Start, commentInfo.BlockCommentEndString);
                 InsertText(textChanges, selectedSpan.Start, commentInfo.BlockCommentStartString);
@@ -199,7 +201,8 @@ protected override void SetTrackingSpans(ITextView textView, ITextBuffer buffer,
             }
 
             // If the end is commented (and not a comment marker), close the current comment and open a new one.
-            if (blockCommentSelectionHelper.IsLocationCommented(selectedSpan.End) && !blockCommentSelectionHelper.DoesEndWithBlockComment(commentInfo))
+            if (blockCommentSelectionHelper.IsLocationCommented(selectedSpan.End)
+                && !blockCommentSelectionHelper.DoesEndWithBlockComment(commentInfo))
             {
                 InsertText(textChanges, selectedSpan.End, commentInfo.BlockCommentEndString);
                 InsertText(textChanges, selectedSpan.End, commentInfo.BlockCommentStartString);
@@ -207,7 +210,8 @@ protected override void SetTrackingSpans(ITextView textView, ITextBuffer buffer,
                 amountToAddToEnd = -commentInfo.BlockCommentStartString.Length;
             }
 
-            trackingSpans.Add(blockCommentSelectionHelper.GetTrackingSpan(selectedSpan, spanTrackingMode, Operation.Comment, amountToAddToStart, amountToAddToEnd));
+            var trackingSpan = blockCommentSelectionHelper.GetTrackingSpan(selectedSpan, spanTrackingMode, amountToAddToStart, amountToAddToEnd);
+            trackingSpans.Add(trackingSpan);
         }
 
         private static void AddBlockComment(CommentSelectionInfo commentInfo, Span span, List<TextChange> textChanges)
@@ -216,14 +220,14 @@ private static void AddBlockComment(CommentSelectionInfo commentInfo, Span span,
             InsertText(textChanges, span.End, commentInfo.BlockCommentEndString);
         }
 
-        private static void DeleteBlockComment(BlockCommentSelectionHelper blockCommentSelectionHelper, Span spanToRemove, List<TextChange> textChanges,
-            CommentSelectionInfo commentInfo)
+        private static void DeleteBlockComment(BlockCommentSelectionHelper blockCommentSelectionHelper, Span spanToRemove,
+            List<TextChange> textChanges, CommentSelectionInfo commentInfo)
         {
             DeleteText(textChanges, new TextSpan(spanToRemove.Start, commentInfo.BlockCommentStartString.Length));
-
             var blockCommentMarkerPosition = spanToRemove.End - commentInfo.BlockCommentEndString.Length;
             // Sometimes the block comment will be missing a close marker.
-            if (Equals(blockCommentSelectionHelper.GetSubstringFromText(blockCommentMarkerPosition, commentInfo.BlockCommentEndString.Length), commentInfo.BlockCommentEndString))
+            if (Equals(blockCommentSelectionHelper.GetSubstringFromText(blockCommentMarkerPosition, commentInfo.BlockCommentEndString.Length),
+                commentInfo.BlockCommentEndString))
             {
                 DeleteText(textChanges, new TextSpan(blockCommentMarkerPosition, commentInfo.BlockCommentEndString.Length));
             }
@@ -317,7 +321,7 @@ public bool DoesEndWithBlockComment(CommentSelectionInfo commentInfo)
             /// </summary>
             public bool IsEntirelyCommented()
             {
-                return !UncommentedSpansInSelection.Any();
+                return !UncommentedSpansInSelection.Any() && HasIntersectingBlockComments();
             }
 
             /// <summary>
@@ -336,11 +340,11 @@ public string GetSubstringFromText(int position, int length)
             /// <summary>
             /// Returns a tracking span associated with the selected span.
             /// </summary>
-            public CommentTrackingSpan GetTrackingSpan(Span span, SpanTrackingMode spanTrackingMode, Operation operation,
+            public CommentTrackingSpan GetTrackingSpan(Span span, SpanTrackingMode spanTrackingMode,
                 int addToStart = 0, int addToEnd = 0)
             {
                 var trackingSpan = SelectedSpan.Snapshot.CreateTrackingSpan(Span.FromBounds(span.Start, span.End), spanTrackingMode);
-                return new CommentTrackingSpan(trackingSpan, operation, addToStart, addToEnd);
+                return new CommentTrackingSpan(trackingSpan, addToStart, addToEnd);
             }
 
             /// <summary>
@@ -355,7 +359,9 @@ public bool TryGetBlockCommentOnSameLine(IEnumerable<Span> allBlockComments, out
                 var caretToLineEndIsWhitespace = IsSpanWhitespace(Span.FromBounds(SelectedSpan.Start, selectedLine.End));
                 foreach (var blockComment in allBlockComments)
                 {
-                    if (lineStartToCaretIsWhitespace && SelectedSpan.Start < blockComment.Start && SelectedSpan.Snapshot.AreOnSameLine(SelectedSpan.Start, blockComment.Start))
+                    if (lineStartToCaretIsWhitespace
+                        && SelectedSpan.Start < blockComment.Start
+                        && SelectedSpan.Snapshot.AreOnSameLine(SelectedSpan.Start, blockComment.Start))
                     {
                         if (IsSpanWhitespace(Span.FromBounds(SelectedSpan.Start, blockComment.Start)))
                         {
@@ -363,7 +369,9 @@ public bool TryGetBlockCommentOnSameLine(IEnumerable<Span> allBlockComments, out
                             return true;
                         }
                     }
-                    else if (caretToLineEndIsWhitespace && SelectedSpan.Start > blockComment.End && SelectedSpan.Snapshot.AreOnSameLine(SelectedSpan.Start, blockComment.End))
+                    else if (caretToLineEndIsWhitespace
+                             && SelectedSpan.Start > blockComment.End
+                             && SelectedSpan.Snapshot.AreOnSameLine(SelectedSpan.Start, blockComment.End))
                     {
                         if (IsSpanWhitespace(Span.FromBounds(blockComment.End, SelectedSpan.Start)))
                         {

src/EditorFeatures/CSharpTest/CommentSelection/ToggleBlockCommentCommandHandlerTests.cs

@@ -26,22 +26,6 @@ namespace Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.CommentSelection
     [UseExportProvider]
     public class ToggleBlockCommentCommandHandlerTests
     {
-        private const string BlockCommentOpenMarker = "/*";
-        private const string BlockCommentCloseMarker = "*/";
-
-        private class MockCommentSelectionService : AbstractCommentSelectionService
-        {
-            public MockCommentSelectionService()
-            {
-                SupportsBlockComment = true;
-            }
-
-            public override string SingleLineCommentString => "//";
-            public override bool SupportsBlockComment { get; }
-            public override string BlockCommentStartString => BlockCommentOpenMarker;
-            public override string BlockCommentEndString => BlockCommentCloseMarker;
-        }
-
         [WpfFact, Trait(Traits.Feature, Traits.Features.ToggleBlockComment)]
         public void AddComment_EmptyCaret()
         {
@@ -1948,7 +1932,7 @@ private static void ToggleBlockCommentMultiple(string markup, string[] expectedT
 
                 for (var i = 0; i < expectedText.Length; i++)
                 {
-                    commandHandler.ExecuteCommand(textView, textBuffer, Operation.Toggle, TestCommandExecutionContext.Create());
+                    commandHandler.ExecuteCommand(textView, textBuffer, Operation.Undefined, TestCommandExecutionContext.Create());
                     AssertCommentResult(doc.TextBuffer, textView, expectedText[i], expectedSelections[i]);
                 }
             }

src/EditorFeatures/Core/EditorFeaturesResources.Designer.cs

@@ -1900,11 +1900,11 @@ internal class EditorFeaturesResources {
         }
         
         /// <summary>
-        ///   Looks up a localized string similar to Toggling block comment on selection....
+        ///   Looks up a localized string similar to Toggling block comment....
         /// </summary>
-        internal static string Toggling_block_comment_on_selection {
+        internal static string Toggling_block_comment {
             get {
-                return ResourceManager.GetString("Toggling_block_comment_on_selection", resourceCulture);
+                return ResourceManager.GetString("Toggling_block_comment", resourceCulture);
             }
         }
         

src/EditorFeatures/Core/EditorFeaturesResources.resx

@@ -892,7 +892,7 @@ Do you want to proceed?</value>
   <data name="Toggle_Block_Comment" xml:space="preserve">
     <value>Toggle Block Comment</value>
   </data>
-  <data name="Toggling_block_comment_on_selection" xml:space="preserve">
-    <value>Toggling block comment on selection...</value>
+  <data name="Toggling_block_comment" xml:space="preserve">
+    <value>Toggling block comment...</value>
   </data>
 </root>
\ No newline at end of file

src/EditorFeatures/Core/Implementation/CommentSelection/AbstractCommentSelectionCommandHandler.cs → src/EditorFeatures/Core/Implementation/CommentSelection/AbstractCommentSelectionBase.cs

@@ -4,6 +4,7 @@
 using System.Collections.Immutable;
 using System.Linq;
 using System.Threading;
+using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.CommentSelection;
 using Microsoft.CodeAnalysis.Editor.Shared.Extensions;
 using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
@@ -18,14 +19,30 @@
 
 namespace Microsoft.CodeAnalysis.Editor.Implementation.CommentSelection
 {
-    internal enum Operation { Comment, Uncomment, Toggle }
+    internal enum Operation
+    {
+        /// <summary>
+        /// The operation is a comment action.
+        /// </summary>
+        Comment,
+
+        /// <summary>
+        /// The operation is an uncomment action.
+        /// </summary>
+        Uncomment,
+
+        /// <summary>
+        /// The operation is not yet determined.
+        /// </summary>
+        Undefined
+    }
 
-    abstract class AbstractCommentSelectionCommandHandler
+    internal abstract partial class AbstractCommentSelectionBase
     {
-        protected readonly ITextUndoHistoryRegistry _undoHistoryRegistry;
-        protected readonly IEditorOperationsFactoryService _editorOperationsFactoryService;
+        private readonly ITextUndoHistoryRegistry _undoHistoryRegistry;
+        private readonly IEditorOperationsFactoryService _editorOperationsFactoryService;
 
-        internal AbstractCommentSelectionCommandHandler(
+        internal AbstractCommentSelectionBase(
             ITextUndoHistoryRegistry undoHistoryRegistry,
             IEditorOperationsFactoryService editorOperationsFactoryService)
         {
@@ -36,14 +53,21 @@ abstract class AbstractCommentSelectionCommandHandler
             _editorOperationsFactoryService = editorOperationsFactoryService;
         }
 
+        public abstract string DisplayName { get; }
+
+        protected abstract string GetTitle(Operation operation);
+
+        protected abstract string GetMessage(Operation operation);
+
+        internal abstract Task<CommentSelectionResult> CollectEdits(
+            Document document, ICommentSelectionService service, NormalizedSnapshotSpanCollection selectedSpans,
+            Operation operation, CancellationToken cancellationToken);
+
         protected static VSCommanding.CommandState GetCommandState(ITextBuffer buffer)
         {
-            if (!buffer.CanApplyChangeDocumentToWorkspace())
-            {
-                return VSCommanding.CommandState.Unspecified;
-            }
-
-            return VSCommanding.CommandState.Available;
+            return buffer.CanApplyChangeDocumentToWorkspace()
+                ? VSCommanding.CommandState.Available
+                : VSCommanding.CommandState.Unspecified;
         }
 
         protected static void Format(ICommentSelectionService service, ITextSnapshot snapshot, IEnumerable<CommentTrackingSpan> changes, CancellationToken cancellationToken)
@@ -54,10 +78,8 @@ protected static void Format(ICommentSelectionService service, ITextSnapshot sna
                 return;
             }
 
-            // Only format uncomment actions.
             var textSpans = changes
-                .Where(change => change.Operation == Operation.Uncomment)
-                .Select(uncommentChange => uncommentChange.ToSnapshotSpan(snapshot).Span.ToTextSpan())
+                .Select(change => change.ToSnapshotSpan(snapshot).Span.ToTextSpan())
                 .ToImmutableArray();
             var newDocument = service.FormatAsync(document, textSpans, cancellationToken).WaitAndGetResult(cancellationToken);
             newDocument.Project.Solution.Workspace.ApplyDocumentChanges(newDocument, cancellationToken);
@@ -78,8 +100,15 @@ internal bool ExecuteCommand(ITextView textView, ITextBuffer subjectBuffer, Oper
             var title = GetTitle(operation);
             var message = GetMessage(operation);
 
-            using (context.OperationContext.AddScope(allowCancellation: false, message))
+            using (context.OperationContext.AddScope(allowCancellation: true, message))
             {
+                var cancellationToken = context.OperationContext.UserCancellationToken;
+
+                var selectedSpans = textView.Selection.GetSnapshotSpansOnBuffer(subjectBuffer);
+                if (selectedSpans.IsEmpty())
+                {
+                    return true;
+                }
 
                 var document = subjectBuffer.CurrentSnapshot.GetOpenDocumentInCurrentContextWithChanges();
                 if (document == null)
@@ -93,27 +122,30 @@ internal bool ExecuteCommand(ITextView textView, ITextBuffer subjectBuffer, Oper
                     return true;
                 }
 
-                var trackingSpans = new List<CommentTrackingSpan>();
-                var textChanges = new List<TextChange>();
-                CollectEdits(
-                    document, service, textView.Selection.GetSnapshotSpansOnBuffer(subjectBuffer),
-                    textChanges, trackingSpans, operation, CancellationToken.None);
+                var edits = CollectEdits(document, service, selectedSpans, operation, cancellationToken).WaitAndGetResult(cancellationToken);
 
+                // Apply the text changes.
                 using (var transaction = new CaretPreservingEditTransaction(title, textView, _undoHistoryRegistry, _editorOperationsFactoryService))
                 {
-                    document.Project.Solution.Workspace.ApplyTextChanges(document.Id, textChanges.Distinct(), CancellationToken.None);
+                    document.Project.Solution.Workspace.ApplyTextChanges(document.Id, edits.TextChanges.Distinct(), cancellationToken);
                     transaction.Complete();
                 }
 
-                using (var transaction = new CaretPreservingEditTransaction(title, textView, _undoHistoryRegistry, _editorOperationsFactoryService))
+                if (edits.ResultOperation == Operation.Uncomment)
                 {
-                    Format(service, subjectBuffer.CurrentSnapshot, trackingSpans, CancellationToken.None);
-                    transaction.Complete();
+                    // Format the document only during uncomment operations.  Use second transaction so it can be undone.
+                    using (var transaction = new CaretPreservingEditTransaction(title, textView, _undoHistoryRegistry, _editorOperationsFactoryService))
+                    {
+                        Format(service, subjectBuffer.CurrentSnapshot, edits.TrackingSpans, cancellationToken);
+                        transaction.Complete();
+                    }
                 }
 
-                if (trackingSpans.Any())
+                // Set the selection after the edits have been applied.
+                if (edits.TrackingSpans.Any())
                 {
-                    SetTrackingSpans(textView, subjectBuffer, trackingSpans);
+                    var spans = edits.TrackingSpans.Select(trackingSpan => trackingSpan.ToSelection(subjectBuffer));
+                    textView.GetMultiSelectionBroker().SetSelectionRange(spans, spans.Last());
                 }
             }
 
@@ -140,17 +172,5 @@ private static ICommentSelectionService GetService(Document document)
 
             return null;
         }
-
-        public abstract string DisplayName { get; }
-
-        protected abstract string GetTitle(Operation operation);
-
-        protected abstract string GetMessage(Operation operation);
-
-        protected abstract void SetTrackingSpans(ITextView textView, ITextBuffer buffer, List<CommentTrackingSpan> trackingSpans);
-
-        internal abstract void CollectEdits(
-            Document document, ICommentSelectionService service, NormalizedSnapshotSpanCollection selectedSpans,
-            List<TextChange> textChanges, List<CommentTrackingSpan> trackingSpans, Operation operation, CancellationToken cancellationToken);
     }
 }

src/EditorFeatures/Core/Implementation/CommentSelection/CommentSelectionResult.cs

+// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
+
+using System.Collections.Generic;
+using Microsoft.CodeAnalysis.Text;
+
+namespace Microsoft.CodeAnalysis.Editor.Implementation.CommentSelection
+{
+    internal struct CommentSelectionResult
+    {
+        /// <summary>
+        /// Text changes to make for this operation.
+        /// </summary>
+        public IEnumerable<TextChange> TextChanges { get; }
+        /// <summary>
+        /// Tracking spans used to format and set the output selection after edits.
+        /// </summary>
+        public IEnumerable<CommentTrackingSpan> TrackingSpans { get; }
+        /// <summary>
+        /// The type of text changes being made.
+        /// </summary>
+        public Operation ResultOperation { get; }
+
+        public CommentSelectionResult(IEnumerable<TextChange> textChanges, IEnumerable<CommentTrackingSpan> trackingSpans, Operation resultOperation)
+        {
+            TextChanges = textChanges;
+            TrackingSpans = trackingSpans;
+            ResultOperation = resultOperation;
+        }
+    }
+}

src/EditorFeatures/Core/Implementation/CommentSelection/CommentTrackingSpan.cs

@@ -9,8 +9,6 @@ namespace Microsoft.CodeAnalysis.Editor.Implementation.CommentSelection
     /// </summary>
     internal struct CommentTrackingSpan
     {
-        public Operation Operation { get; }
-
         private readonly ITrackingSpan _trackingSpan;
 
         // In some cases, the tracking span needs to be adjusted by a specific amount after the changes have been applied.
@@ -18,17 +16,15 @@ internal struct CommentTrackingSpan
         private readonly int _amountToAddToStart;
         private readonly int _amountToAddToEnd;
 
-        public CommentTrackingSpan(ITrackingSpan trackingSpan, Operation operation)
+        public CommentTrackingSpan(ITrackingSpan trackingSpan)
         {
-            Operation = operation;
             _trackingSpan = trackingSpan;
             _amountToAddToStart = 0;
             _amountToAddToEnd = 0;
         }
 
-        public CommentTrackingSpan(ITrackingSpan trackingSpan, Operation operation, int amountToAddToStart, int amountToAddToEnd)
+        public CommentTrackingSpan(ITrackingSpan trackingSpan, int amountToAddToStart, int amountToAddToEnd)
         {
-            Operation = operation;
             _trackingSpan = trackingSpan;
             _amountToAddToStart = amountToAddToStart;
             _amountToAddToEnd = amountToAddToEnd;
@@ -44,8 +40,12 @@ public SnapshotSpan ToSnapshotSpan(ITextSnapshot snapshot)
             var snapshotSpan = _trackingSpan.GetSpan(snapshot);
             if (_amountToAddToStart != 0 || _amountToAddToEnd != 0)
             {
-                var spanExpandedByAmount = Span.FromBounds(snapshotSpan.Start.Position + _amountToAddToStart, snapshotSpan.End.Position + _amountToAddToEnd);
-                snapshotSpan = new SnapshotSpan(snapshot, spanExpandedByAmount);
+                var updatedStart = snapshotSpan.Start.Position + _amountToAddToStart;
+                var updatedEnd = snapshotSpan.End.Position + _amountToAddToEnd;
+                if (updatedStart >= snapshotSpan.Start.Position && updatedEnd <= snapshotSpan.End.Position)
+                {
+                    snapshotSpan = new SnapshotSpan(snapshot, Span.FromBounds(updatedStart, updatedEnd));
+                }
             }
 
             return snapshotSpan;

src/EditorFeatures/Core/Implementation/CommentSelection/CommentUncommentSelectionCommandHandler.cs

@@ -6,6 +6,7 @@
 using System.ComponentModel.Composition;
 using System.Linq;
 using System.Threading;
+using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.CommentSelection;
 using Microsoft.CodeAnalysis.Editor.Shared.Extensions;
 using Microsoft.CodeAnalysis.Shared.Extensions;
@@ -22,19 +23,21 @@
 
 namespace Microsoft.CodeAnalysis.Editor.Implementation.CommentSelection
 {
-    [Export(typeof(VSCommanding.ICommandHandler))]
-    [ContentType(ContentTypeNames.RoslynContentType)]
-    [Name(PredefinedCommandHandlerNames.CommentSelection)]
+    //[Export(typeof(VSCommanding.ICommandHandler))]
+    //[ContentType(ContentTypeNames.RoslynContentType)]
+    //[Name(PredefinedCommandHandlerNames.CommentSelection)]
     internal class CommentUncommentSelectionCommandHandler :
-        AbstractCommentSelectionCommandHandler,
+        AbstractCommentSelectionBase,
         VSCommanding.ICommandHandler<CommentSelectionCommandArgs>,
         VSCommanding.ICommandHandler<UncommentSelectionCommandArgs>
     {
         [ImportingConstructor]
         internal CommentUncommentSelectionCommandHandler(
             ITextUndoHistoryRegistry undoHistoryRegistry,
-            IEditorOperationsFactoryService editorOperationsFactoryService) : base(undoHistoryRegistry, editorOperationsFactoryService)
-        { }
+            IEditorOperationsFactoryService editorOperationsFactoryService)
+            : base(undoHistoryRegistry, editorOperationsFactoryService)
+        {
+        }
 
         public VSCommanding.CommandState GetCommandState(CommentSelectionCommandArgs args)
         {
@@ -66,32 +69,29 @@ public bool ExecuteCommand(UncommentSelectionCommandArgs args, CommandExecutionC
 
         protected override string GetTitle(Operation operation)
         {
-            return operation == Operation.Comment ? EditorFeaturesResources.Comment_Selection
+            return operation == Operation.Comment
+                ? EditorFeaturesResources.Comment_Selection
                 : EditorFeaturesResources.Uncomment_Selection;
         }
 
         protected override string GetMessage(Operation operation)
         {
-            return operation == Operation.Comment ? EditorFeaturesResources.Commenting_currently_selected_text
+            return operation == Operation.Comment
+                ? EditorFeaturesResources.Commenting_currently_selected_text
                 : EditorFeaturesResources.Uncommenting_currently_selected_text;
         }
 
-        protected override void SetTrackingSpans(ITextView textView, ITextBuffer buffer, List<CommentTrackingSpan> trackingSpans)
-        {
-            // TODO, this doesn't currently handle block selection
-            textView.SetSelection(trackingSpans.First().ToSnapshotSpan(buffer.CurrentSnapshot));
-        }
-
         /// <summary>
         /// Add the necessary edits to the given spans. Also collect tracking spans over each span.
         ///
         /// Internal so that it can be called by unit tests.
         /// </summary>
-        internal override void CollectEdits(
+        internal override Task<CommentSelectionResult> CollectEdits(
             Document document, ICommentSelectionService service, NormalizedSnapshotSpanCollection selectedSpans,
-            List<TextChange> textChanges, List<CommentTrackingSpan> trackingSpans, Operation operation, CancellationToken cancellationToken)
+            Operation operation, CancellationToken cancellationToken)
         {
             var spanTrackingList = new List<ITrackingSpan>();
+            var textChanges = new List<TextChange>();
             foreach (var span in selectedSpans)
             {
                 if (operation == Operation.Comment)
@@ -103,7 +103,7 @@ protected override void SetTrackingSpans(ITextView textView, ITextBuffer buffer,
                     UncommentSpan(document, service, span, textChanges, spanTrackingList, cancellationToken);
                 }
             }
-            trackingSpans.AddRange(spanTrackingList.Select(span => new CommentTrackingSpan(span, operation)));
+            return Task.FromResult(new CommentSelectionResult(textChanges, spanTrackingList.Select(span => new CommentTrackingSpan(span)), operation));
         }
 
         /// <summary>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.cs.xlf

@@ -1284,9 +1284,9 @@ Chcete pokračovat?</target>
         <target state="translated">Inteligentní formátování tokenů</target>
         <note />
       </trans-unit>
-      <trans-unit id="Toggling_block_comment_on_selection">
-        <source>Toggling block comment on selection...</source>
-        <target state="new">Toggling block comment on selection...</target>
+      <trans-unit id="Toggling_block_comment">
+        <source>Toggling block comment...</source>
+        <target state="new">Toggling block comment...</target>
         <note />
       </trans-unit>
       <trans-unit id="Toggle_Block_Comment">

src/EditorFeatures/Core/xlf/EditorFeaturesResources.de.xlf

@@ -1284,9 +1284,9 @@ Möchten Sie fortfahren?</target>
         <target state="translated">Intelligente Tokenformatierung</target>
         <note />
       </trans-unit>
-      <trans-unit id="Toggling_block_comment_on_selection">
-        <source>Toggling block comment on selection...</source>
-        <target state="new">Toggling block comment on selection...</target>
+      <trans-unit id="Toggling_block_comment">
+        <source>Toggling block comment...</source>
+        <target state="new">Toggling block comment...</target>
         <note />
       </trans-unit>
       <trans-unit id="Toggle_Block_Comment">

src/EditorFeatures/Core/xlf/EditorFeaturesResources.es.xlf

@@ -1284,9 +1284,9 @@ Do you want to proceed?</source>
         <target state="translated">Formateador de token inteligente</target>
         <note />
       </trans-unit>
-      <trans-unit id="Toggling_block_comment_on_selection">
-        <source>Toggling block comment on selection...</source>
-        <target state="new">Toggling block comment on selection...</target>
+      <trans-unit id="Toggling_block_comment">
+        <source>Toggling block comment...</source>
+        <target state="new">Toggling block comment...</target>
         <note />
       </trans-unit>
       <trans-unit id="Toggle_Block_Comment">

src/EditorFeatures/Core/xlf/EditorFeaturesResources.fr.xlf

@@ -1284,9 +1284,9 @@ Voulez-vous continuer ?</target>
         <target state="translated">Formateur de jeton intelligent</target>
         <note />
       </trans-unit>
-      <trans-unit id="Toggling_block_comment_on_selection">
-        <source>Toggling block comment on selection...</source>
-        <target state="new">Toggling block comment on selection...</target>
+      <trans-unit id="Toggling_block_comment">
+        <source>Toggling block comment...</source>
+        <target state="new">Toggling block comment...</target>
         <note />
       </trans-unit>
       <trans-unit id="Toggle_Block_Comment">

src/EditorFeatures/Core/xlf/EditorFeaturesResources.it.xlf

@@ -1284,9 +1284,9 @@ Continuare?</target>
         <target state="translated">Formattatore di token intelligente</target>
         <note />
       </trans-unit>
-      <trans-unit id="Toggling_block_comment_on_selection">
-        <source>Toggling block comment on selection...</source>
-        <target state="new">Toggling block comment on selection...</target>
+      <trans-unit id="Toggling_block_comment">
+        <source>Toggling block comment...</source>
+        <target state="new">Toggling block comment...</target>
         <note />
       </trans-unit>
       <trans-unit id="Toggle_Block_Comment">

src/EditorFeatures/Core/xlf/EditorFeaturesResources.ja.xlf

@@ -1284,9 +1284,9 @@ Do you want to proceed?</source>
         <target state="translated">スマート トークン フォーマッタ</target>
         <note />
       </trans-unit>
-      <trans-unit id="Toggling_block_comment_on_selection">
-        <source>Toggling block comment on selection...</source>
-        <target state="new">Toggling block comment on selection...</target>
+      <trans-unit id="Toggling_block_comment">
+        <source>Toggling block comment...</source>
+        <target state="new">Toggling block comment...</target>
         <note />
       </trans-unit>
       <trans-unit id="Toggle_Block_Comment">

src/EditorFeatures/Core/xlf/EditorFeaturesResources.ko.xlf

@@ -1284,9 +1284,9 @@ Do you want to proceed?</source>
         <target state="translated">스마트 토큰 포맷터</target>
         <note />
       </trans-unit>
-      <trans-unit id="Toggling_block_comment_on_selection">
-        <source>Toggling block comment on selection...</source>
-        <target state="new">Toggling block comment on selection...</target>
+      <trans-unit id="Toggling_block_comment">
+        <source>Toggling block comment...</source>
+        <target state="new">Toggling block comment...</target>
         <note />
       </trans-unit>
       <trans-unit id="Toggle_Block_Comment">

src/EditorFeatures/Core/xlf/EditorFeaturesResources.pl.xlf

@@ -1284,9 +1284,9 @@ Czy chcesz kontynuować?</target>
         <target state="translated">Inteligentny element formatujący tokeny</target>
         <note />
       </trans-unit>
-      <trans-unit id="Toggling_block_comment_on_selection">
-        <source>Toggling block comment on selection...</source>
-        <target state="new">Toggling block comment on selection...</target>
+      <trans-unit id="Toggling_block_comment">
+        <source>Toggling block comment...</source>
+        <target state="new">Toggling block comment...</target>
         <note />
       </trans-unit>
       <trans-unit id="Toggle_Block_Comment">

src/EditorFeatures/Core/xlf/EditorFeaturesResources.pt-BR.xlf

@@ -1284,9 +1284,9 @@ Deseja continuar?</target>
         <target state="translated">Formatador de Token Inteligente</target>
         <note />
       </trans-unit>
-      <trans-unit id="Toggling_block_comment_on_selection">
-        <source>Toggling block comment on selection...</source>
-        <target state="new">Toggling block comment on selection...</target>
+      <trans-unit id="Toggling_block_comment">
+        <source>Toggling block comment...</source>
+        <target state="new">Toggling block comment...</target>
         <note />
       </trans-unit>
       <trans-unit id="Toggle_Block_Comment">

src/EditorFeatures/Core/xlf/EditorFeaturesResources.ru.xlf

@@ -1284,9 +1284,9 @@ Do you want to proceed?</source>
         <target state="translated">Средство форматирования смарт-токена</target>
         <note />
       </trans-unit>
-      <trans-unit id="Toggling_block_comment_on_selection">
-        <source>Toggling block comment on selection...</source>
-        <target state="new">Toggling block comment on selection...</target>
+      <trans-unit id="Toggling_block_comment">
+        <source>Toggling block comment...</source>
+        <target state="new">Toggling block comment...</target>
         <note />
       </trans-unit>
       <trans-unit id="Toggle_Block_Comment">

src/EditorFeatures/Core/xlf/EditorFeaturesResources.tr.xlf

@@ -1284,9 +1284,9 @@ Devam etmek istiyor musunuz?</target>
         <target state="translated">Akıllı Belirteç Biçimlendirici</target>
         <note />
       </trans-unit>
-      <trans-unit id="Toggling_block_comment_on_selection">
-        <source>Toggling block comment on selection...</source>
-        <target state="new">Toggling block comment on selection...</target>
+      <trans-unit id="Toggling_block_comment">
+        <source>Toggling block comment...</source>
+        <target state="new">Toggling block comment...</target>
         <note />
       </trans-unit>
       <trans-unit id="Toggle_Block_Comment">

src/EditorFeatures/Core/xlf/EditorFeaturesResources.zh-Hans.xlf

@@ -1284,9 +1284,9 @@ Do you want to proceed?</source>
         <target state="translated">智能令牌格式化程序</target>
         <note />
       </trans-unit>
-      <trans-unit id="Toggling_block_comment_on_selection">
-        <source>Toggling block comment on selection...</source>
-        <target state="new">Toggling block comment on selection...</target>
+      <trans-unit id="Toggling_block_comment">
+        <source>Toggling block comment...</source>
+        <target state="new">Toggling block comment...</target>
         <note />
       </trans-unit>
       <trans-unit id="Toggle_Block_Comment">

src/EditorFeatures/Core/xlf/EditorFeaturesResources.zh-Hant.xlf

@@ -1284,9 +1284,9 @@ Do you want to proceed?</source>
         <target state="translated">智慧權杖格式器</target>
         <note />
       </trans-unit>
-      <trans-unit id="Toggling_block_comment_on_selection">
-        <source>Toggling block comment on selection...</source>
-        <target state="new">Toggling block comment on selection...</target>
+      <trans-unit id="Toggling_block_comment">
+        <source>Toggling block comment...</source>
+        <target state="new">Toggling block comment...</target>
         <note />
       </trans-unit>
       <trans-unit id="Toggle_Block_Comment">

src/EditorFeatures/Test/CommentSelection/CommentUncommentSelectionCommandHandlerTests.cs

@@ -767,26 +767,22 @@ private static void CommentSelection(ITextView textView, IEnumerable<TextChange>
             var commandHandler = new CommentUncommentSelectionCommandHandler(textUndoHistoryRegistry, editorOperationsFactory);
             var service = new MockCommentSelectionService(supportBlockComments);
 
-            var trackingSpans = new List<CommentTrackingSpan>();
-            var textChanges = new List<TextChange>();
+            var edits = commandHandler.CollectEdits(
+                null, service, textView.Selection.GetSnapshotSpansOnBuffer(textView.TextBuffer), operation, CancellationToken.None).WaitAndGetResult(CancellationToken.None);
 
-            commandHandler.CollectEdits(
-                null, service, textView.Selection.GetSnapshotSpansOnBuffer(textView.TextBuffer),
-                textChanges, trackingSpans, operation, CancellationToken.None);
-
-            Roslyn.Test.Utilities.AssertEx.SetEqual(expectedChanges, textChanges);
+            Roslyn.Test.Utilities.AssertEx.SetEqual(expectedChanges, edits.TextChanges);
 
             // Actually apply the edit to let the tracking spans adjust.
             using (var edit = textView.TextBuffer.CreateEdit())
             {
-                textChanges.Do(tc => edit.Replace(tc.Span.ToSpan(), tc.NewText));
+                edits.TextChanges.Do(tc => edit.Replace(tc.Span.ToSpan(), tc.NewText));
 
                 edit.Apply();
             }
 
-            if (trackingSpans.Any())
+            if (edits.TrackingSpans.Any())
             {
-                textView.SetSelection(trackingSpans.First().ToSnapshotSpan(textView.TextBuffer.CurrentSnapshot));
+                textView.SetSelection(edits.TrackingSpans.First().ToSnapshotSpan(textView.TextBuffer.CurrentSnapshot));
             }
 
             if (expectedSelectedSpans != null)

src/Features/Core/Portable/CommentSelection/ICommentSelectionService.cs

 // Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
+using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Threading;
 using System.Threading.Tasks;
@@ -14,4 +15,13 @@ internal interface ICommentSelectionService : ILanguageService
 
         Task<Document> FormatAsync(Document document, ImmutableArray<TextSpan> changes, CancellationToken cancellationToken);
     }
+
+    internal interface ICommentSelectionLanguageService : ILanguageService
+    {
+        Task<CommentSelectionInfo> GetInfoAsync(Document document, TextSpan textSpan, CancellationToken cancellationToken);
+
+        Task<Document> FormatAsync(Document document, ImmutableArray<TextSpan> changes, CancellationToken cancellationToken);
+
+        Task<Document> ToggleBlockComment(Document document, IEnumerable<TextSpan> selectedSpans, CancellationToken cancellationToken);
+    }
 }