Fix issue where we were querying a linq expression over and over

src/EditorFeatures/Core/Shared/Extensions/HostWorkspaceServicesExtensions.cs

@@ -25,12 +25,10 @@ internal static class HostWorkspaceServicesExtensions
         public static CodeAnalysis.Host.LanguageServices? GetProjectServices(
             this SolutionServices workspaceServices, IContentType contentType)
         {
-            foreach (var language in workspaceServices.SupportedLanguages)
+            foreach (var language in workspaceServices.SupportedLanguagesArray)
             {
                 if (LanguageMatches(language, contentType, workspaceServices))
-                {
                     return workspaceServices.GetLanguageServices(language);
-                }
             }
 
             return null;

src/Workspaces/Core/Portable/Workspace/Host/HostWorkspaceServices.cs

@@ -4,6 +4,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using Microsoft.CodeAnalysis.Text;
 
 namespace Microsoft.CodeAnalysis.Host;
@@ -86,7 +87,9 @@ internal virtual ITextFactoryService TextFactory
     /// <summary>
     /// A list of language names for supported language services.
     /// </summary>
-    public virtual IEnumerable<string> SupportedLanguages => [];
+    public virtual IEnumerable<string> SupportedLanguages => SupportedLanguagesArray;
+
+    internal virtual ImmutableArray<string> SupportedLanguagesArray => [];
 
     /// <summary>
     /// Returns true if the language is supported.

src/Workspaces/Core/Portable/Workspace/Host/SolutionServices.cs

@@ -4,6 +4,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using Microsoft.CodeAnalysis.Host.Mef;
 
 namespace Microsoft.CodeAnalysis.Host;
@@ -43,6 +44,9 @@ public TWorkspaceService GetRequiredService<TWorkspaceService>() where TWorkspac
     public IEnumerable<string> SupportedLanguages
         => _services.SupportedLanguages;
 
+    internal ImmutableArray<string> SupportedLanguagesArray
+        => _services.SupportedLanguagesArray;
+
     /// <inheritdoc cref="HostWorkspaceServices.IsSupported"/>
     public bool IsSupported(string languageName)
         => _services.IsSupported(languageName);

src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Workspace/Mef/MefWorkspaceServices.cs

@@ -32,6 +32,8 @@
         private ImmutableDictionary<string, MefLanguageServices> _languageServicesMap
             = ImmutableDictionary<string, MefLanguageServices>.Empty;
 
+        private ImmutableArray<string> _languages;
+
         public MefWorkspaceServices(IMefHostExportProvider host, Workspace workspace)
         {
             _exportProvider = host;
@@ -86,29 +88,27 @@
             return service != null;
         }
 
-        private IEnumerable<string>? _languages;
-
-        private IEnumerable<string> GetSupportedLanguages()
+        internal override ImmutableArray<string> SupportedLanguagesArray
         {
-            if (_languages == null)
+            get
             {
-                var list = _exportProvider.GetExports<ILanguageService, LanguageServiceMetadata>().Select(lz => lz.Metadata.Language).Concat(
-                           _exportProvider.GetExports<ILanguageServiceFactory, LanguageServiceMetadata>().Select(lz => lz.Metadata.Language))
-                           .Distinct();
-
-                Interlocked.CompareExchange(ref _languages, list, null);
-            }
+                var localLanguages = _languages;
+                if (localLanguages.IsDefault)
+                {
+                    var list = _exportProvider.GetExports<ILanguageService, LanguageServiceMetadata>().Select(lz => lz.Metadata.Language).Concat(
+                               _exportProvider.GetExports<ILanguageServiceFactory, LanguageServiceMetadata>().Select(lz => lz.Metadata.Language))
+                               .Distinct()
+                               .ToImmutableArray();
 
-            return _languages;
-        }
+                    ImmutableInterlocked.InterlockedCompareExchange(ref _languages, list, localLanguages);
+                }
 
-        public override IEnumerable<string> SupportedLanguages
-        {
-            get { return this.GetSupportedLanguages(); }
+                return _languages;
+            }
         }
 
         public override bool IsSupported(string languageName)
-            => this.GetSupportedLanguages().Contains(languageName);
+            => this.SupportedLanguagesArray.Contains(languageName);
 
         public override HostLanguageServices GetLanguageServices(string languageName)
         {