Code style preview: when no codestyle..

.. is selected, use the first codestyle to show a preview.

src/VisualStudio/CSharp/Impl/Options/Formatting/StyleViewModel.cs

@@ -20,8 +20,6 @@ namespace Microsoft.VisualStudio.LanguageServices.CSharp.Options.Formatting
     /// </remarks>
     internal class StyleViewModel : AbstractOptionPreviewViewModel
     {
-        public ObservableCollection<AbstractCodeStyleOptionViewModel> CodeStyleItems { get; set; }
-
         internal override bool ShouldPersistOption(OptionKey key)
         {
             return key.Option.Feature == CSharpCodeStyleOptions.FeatureName || key.Option.Feature == SimplificationOptions.PerLanguageFeatureName;
@@ -168,8 +166,6 @@ void foo()
 
         internal StyleViewModel(OptionSet optionSet, IServiceProvider serviceProvider) : base(optionSet, serviceProvider, LanguageNames.CSharp)
         {
-            CodeStyleItems = new ObservableCollection<AbstractCodeStyleOptionViewModel>();
-
             var collectionView = (ListCollectionView)CollectionViewSource.GetDefaultView(CodeStyleItems);
             collectionView.GroupDescriptions.Add(new PropertyGroupDescription(nameof(AbstractCodeStyleOptionViewModel.GroupName)));
 

src/VisualStudio/Core/Impl/Options/AbstractOptionPreviewViewModel.cs

@@ -2,6 +2,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Linq;
 using System.Text;
 using System.Threading;
@@ -39,6 +40,7 @@ internal abstract class AbstractOptionPreviewViewModel : AbstractNotifyPropertyC
         private IContentTypeRegistryService _contentTypeRegistryService;
 
         public List<object> Items { get; set; }
+        public ObservableCollection<AbstractCodeStyleOptionViewModel> CodeStyleItems { get; set; }
 
         public OptionSet Options { get; set; }
 
@@ -46,6 +48,7 @@ protected AbstractOptionPreviewViewModel(OptionSet options, IServiceProvider ser
         {
             this.Options = options;
             this.Items = new List<object>();
+            this.CodeStyleItems = new ObservableCollection<AbstractCodeStyleOptionViewModel>();
 
             _componentModel = (IComponentModel)serviceProvider.GetService(typeof(SComponentModel));
 

src/VisualStudio/Core/Impl/Options/GridOptionPreviewControl.xaml.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;
+using System.Linq;
 using System.Windows.Controls;
 using System.Windows.Input;
 using Microsoft.CodeAnalysis.Options;
@@ -56,9 +57,8 @@ internal override void LoadSettings()
         {
             this.ViewModel = _createViewModel(this.OptionService.GetOptions(), _serviceProvider);
 
-            // TODO: Use the first item's preview. This doesn't work yet.
-            // var firstItem = this.ViewModel.Items.OfType<AbstractCodeStyleOptionViewModel>().First();
-            // this.ViewModel.SetOptionAndUpdatePreview(firstItem.SelectedPreference.IsChecked, firstItem.Option, firstItem.GetPreview());
+            var firstItem = this.ViewModel.CodeStyleItems.OfType<AbstractCodeStyleOptionViewModel>().First();
+            this.ViewModel.SetOptionAndUpdatePreview(firstItem.SelectedPreference.IsChecked, firstItem.Option, firstItem.GetPreview());
 
             DataContext = ViewModel;
         }