Make fields readonly

src/EditorFeatures/Core.Wpf/InlineRename/Dashboard/Dashboard.xaml.cs

@@ -29,7 +29,7 @@ internal partial class Dashboard : UserControl, IDisposable
 
         internal bool ShouldReceiveKeyboardNavigation { get; set; }
 
-        private IEnumerable<string> _renameAccessKeys = new[]
+        private readonly IEnumerable<string> _renameAccessKeys = new[]
             {
                 RenameShortcutKey.RenameOverloads,
                 RenameShortcutKey.SearchInComments,

src/EditorFeatures/Core.Wpf/InlineRename/InlineRenameSession.cs

@@ -50,7 +50,7 @@ internal partial class InlineRenameSession : ForegroundThreadAffinitizedObject,
         private bool _isApplyingEdit;
         private string _replacementText;
         private OptionSet _optionSet;
-        private Dictionary<ITextBuffer, OpenTextBufferManager> _openTextBuffers = new Dictionary<ITextBuffer, OpenTextBufferManager>();
+        private readonly Dictionary<ITextBuffer, OpenTextBufferManager> _openTextBuffers = new Dictionary<ITextBuffer, OpenTextBufferManager>();
 
         /// <summary>
         /// If non-null, the current text of the replacement. Linked spans added will automatically be updated with this

src/EditorFeatures/Core.Wpf/NavigateTo/DefaultNavigateToPreviewServiceFactory.cs

@@ -10,7 +10,7 @@ namespace Microsoft.CodeAnalysis.Editor.Implementation.NavigateTo
     [ExportWorkspaceServiceFactory(typeof(INavigateToPreviewService), ServiceLayer.Editor), Shared]
     internal sealed class DefaultNavigateToPreviewServiceFactory : IWorkspaceServiceFactory
     {
-        private Lazy<INavigateToPreviewService> _singleton =
+        private readonly Lazy<INavigateToPreviewService> _singleton =
             new Lazy<INavigateToPreviewService>(() => new DefaultNavigateToPreviewService());
 
         public IWorkspaceService CreateService(HostWorkspaceServices workspaceServices)

src/EditorFeatures/Core.Wpf/Notification/EditorNotificationServiceFactory.cs

@@ -13,7 +13,7 @@ namespace Microsoft.CodeAnalysis.Editor.Implementation.Notification
     [Shared]
     internal class EditorNotificationServiceFactory : IWorkspaceServiceFactory
     {
-        private static object s_gate = new object();
+        private static readonly object s_gate = new object();
 
         private static EditorDialogService s_singleton;
 

src/EditorFeatures/Core.Wpf/Options/LegacyEditorConfigDocumentOptionsProvider.DocumentOptions.cs

@@ -15,7 +15,7 @@ internal sealed partial class LegacyEditorConfigDocumentOptionsProvider : IDocum
     {
         private class DocumentOptions : IDocumentOptions
         {
-            private ICodingConventionsSnapshot _codingConventionSnapshot;
+            private readonly ICodingConventionsSnapshot _codingConventionSnapshot;
             private readonly IErrorLoggerService _errorLogger;
             private static readonly ConditionalWeakTable<IReadOnlyDictionary<string, object>, IReadOnlyDictionary<string, string>> s_convertedDictionaryCache =
                 new ConditionalWeakTable<IReadOnlyDictionary<string, object>, IReadOnlyDictionary<string, string>>();

src/EditorFeatures/Core.Wpf/Structure/AbstractStructureTaggerProvider.cs

@@ -35,7 +35,7 @@ internal abstract partial class AbstractStructureTaggerProvider<TRegionTag> :
         AsynchronousTaggerProvider<TRegionTag>
         where TRegionTag : class, ITag
     {
-        private static IComparer<BlockSpan> s_blockSpanComparer =
+        private static readonly IComparer<BlockSpan> s_blockSpanComparer =
             Comparer<BlockSpan>.Create((s1, s2) => s1.TextSpan.Start - s2.TextSpan.Start);
 
         protected readonly ITextEditorFactoryService TextEditorFactoryService;

src/EditorFeatures/Core.Wpf/SymbolSearch/SymbolSearchUpdateEngine.cs

@@ -25,7 +25,7 @@ namespace Microsoft.CodeAnalysis.SymbolSearch
     /// </summary>
     internal partial class SymbolSearchUpdateEngine : ISymbolSearchUpdateEngine
     {
-        private ConcurrentDictionary<string, IAddReferenceDatabaseWrapper> _sourceToDatabase =
+        private readonly ConcurrentDictionary<string, IAddReferenceDatabaseWrapper> _sourceToDatabase =
             new ConcurrentDictionary<string, IAddReferenceDatabaseWrapper>();
 
         public SymbolSearchUpdateEngine(