diff --git a/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerConfigOptions.cs b/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerConfigOptions.cs
index 430230a273caa357aff61953eaa45c78dedda766..621771f61061882b44029345ded630fabf706745 100644
--- a/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerConfigOptions.cs
+++ b/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerConfigOptions.cs
@@ -22,29 +22,26 @@ public abstract class AnalyzerConfigOptions
         /// Get an analyzer config value for the given key, using the <see cref="KeyComparer"/>.
         /// </summary>
         public abstract bool TryGetValue(string key, out string value);
+
+        /// <summary>
+        /// Get the keys of the defined options.
+        /// </summary>
+        public abstract ImmutableArray<string> Keys { get; }
     }
 
-    public abstract class DictionaryBackedAnalyzerConfigOptions : AnalyzerConfigOptions
+    internal sealed class CompilerAnalyzerConfigOptions : AnalyzerConfigOptions
     {
+        public static CompilerAnalyzerConfigOptions Empty { get; } = new CompilerAnalyzerConfigOptions(EmptyDictionary);
+
         private readonly ImmutableDictionary<string, string> _backing;
 
-        public DictionaryBackedAnalyzerConfigOptions(ImmutableDictionary<string, string> properties)
+        public CompilerAnalyzerConfigOptions(ImmutableDictionary<string, string> properties)
         {
             _backing = properties;
         }
 
         public override bool TryGetValue(string key, out string value) => _backing.TryGetValue(key, out value);
 
-        public IReadOnlyDictionary<string, string> AsReadOnlyDictionary() => _backing;
-    }
-
-    internal sealed class CompilerAnalyzerConfigOptions : DictionaryBackedAnalyzerConfigOptions
-    {
-        public static CompilerAnalyzerConfigOptions Empty { get; } = new CompilerAnalyzerConfigOptions(EmptyDictionary);
-
-        public CompilerAnalyzerConfigOptions(ImmutableDictionary<string, string> properties)
-            : base(properties)
-        {
-        }
+        public override ImmutableArray<string> Keys => _backing.Keys.ToImmutableArray();
     }
 }
diff --git a/src/Compilers/Core/Portable/PublicAPI.Unshipped.txt b/src/Compilers/Core/Portable/PublicAPI.Unshipped.txt
index 78413f9718c17dc24f41c08f778bd0b415404da8..ca589687a62326e30693c08faf067ec18395bddd 100644
--- a/src/Compilers/Core/Portable/PublicAPI.Unshipped.txt
+++ b/src/Compilers/Core/Portable/PublicAPI.Unshipped.txt
@@ -1,8 +1,5 @@
 Microsoft.CodeAnalysis.CommandLineArguments.ErrorLogOptions.get -> Microsoft.CodeAnalysis.ErrorLogOptions
 *REMOVED*Microsoft.CodeAnalysis.CommandLineArguments.ErrorLogPath.get -> string
-Microsoft.CodeAnalysis.Diagnostics.DictionaryBackedAnalyzerConfigOptions
-Microsoft.CodeAnalysis.Diagnostics.DictionaryBackedAnalyzerConfigOptions.AsReadOnlyDictionary() -> System.Collections.Generic.IReadOnlyDictionary<string, string>
-Microsoft.CodeAnalysis.Diagnostics.DictionaryBackedAnalyzerConfigOptions.DictionaryBackedAnalyzerConfigOptions(System.Collections.Immutable.ImmutableDictionary<string, string> properties) -> void
 Microsoft.CodeAnalysis.ErrorLogOptions
 Microsoft.CodeAnalysis.ErrorLogOptions.ErrorLogOptions(string path, Microsoft.CodeAnalysis.SarifVersion sarifVersion) -> void
 Microsoft.CodeAnalysis.ErrorLogOptions.Path.get -> string
@@ -22,7 +19,7 @@ Microsoft.CodeAnalysis.SarifVersion.Latest = 2147483647 -> Microsoft.CodeAnalysi
 Microsoft.CodeAnalysis.SarifVersion.Sarif1 = 1 -> Microsoft.CodeAnalysis.SarifVersion
 Microsoft.CodeAnalysis.SarifVersion.Sarif2 = 2 -> Microsoft.CodeAnalysis.SarifVersion
 Microsoft.CodeAnalysis.SarifVersionFacts
-override Microsoft.CodeAnalysis.Diagnostics.DictionaryBackedAnalyzerConfigOptions.TryGetValue(string key, out string value) -> bool
+abstract Microsoft.CodeAnalysis.Diagnostics.AnalyzerConfigOptions.Keys.get -> System.Collections.Immutable.ImmutableArray<string>
 Microsoft.CodeAnalysis.SymbolDisplayMiscellaneousOptions.IncludeNotNullableReferenceTypeModifier = 256 -> Microsoft.CodeAnalysis.SymbolDisplayMiscellaneousOptions
 static Microsoft.CodeAnalysis.SarifVersionFacts.TryParse(string version, out Microsoft.CodeAnalysis.SarifVersion result) -> bool
 Microsoft.CodeAnalysis.IMethodSymbol.IsConditional.get -> bool
diff --git a/src/Workspaces/Core/Portable/Options/EditorConfig/EditorConfigStorageLocationExtensions.cs b/src/Workspaces/Core/Portable/Options/EditorConfig/EditorConfigStorageLocationExtensions.cs
index 83834252482328b1187e63d1045bd18b8f13ee61..5abc812cba2cf8d6d834b9d24f707d32bf89d4ba 100644
--- a/src/Workspaces/Core/Portable/Options/EditorConfig/EditorConfigStorageLocationExtensions.cs
+++ b/src/Workspaces/Core/Portable/Options/EditorConfig/EditorConfigStorageLocationExtensions.cs
@@ -1,9 +1,9 @@
 // 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.Collections;
-using System.Collections.Generic;
+using System.Collections.Immutable;
 using Microsoft.CodeAnalysis.Diagnostics;
+using Roslyn.Collections.Immutable;
 
 namespace Microsoft.CodeAnalysis.Options
 {
@@ -11,63 +11,15 @@ internal static class EditorConfigStorageLocationExtensions
     {
         public static bool TryGetOption(this IEditorConfigStorageLocation editorConfigStorageLocation, AnalyzerConfigOptions analyzerConfigOptions, Type type, out object value)
         {
-            var optionDictionary = analyzerConfigOptions is DictionaryBackedAnalyzerConfigOptions dictionaryAnalyzerConfigOptions
-                ? dictionaryAnalyzerConfigOptions.AsReadOnlyDictionary()
-                : new AnalyzerConfigOptionsDictionary(analyzerConfigOptions);
-
-            return editorConfigStorageLocation.TryGetOption(optionDictionary, type, out value);
-        }
-
-        /// <summary>
-        /// This is a wrapper around AnalyzerConfigOptions so that it can be used as a read-only Dictionary.
-        /// </summary>
-        private class AnalyzerConfigOptionsDictionary : IReadOnlyDictionary<string, string>
-        {
-            private readonly AnalyzerConfigOptions _analyzerConfigOptions;
-
-            public AnalyzerConfigOptionsDictionary(AnalyzerConfigOptions analyzerConfigOptions)
-            {
-                _analyzerConfigOptions = analyzerConfigOptions;
-            }
-
-            public string this[string key]
-            {
-                get
+            var optionDictionary = analyzerConfigOptions.Keys.ToImmutableDictionary(
+                key => key,
+                key =>
                 {
-                    if (_analyzerConfigOptions.TryGetValue(key, out var value))
-                    {
-                        return value;
-                    }
-
-                    throw new KeyNotFoundException();
-                }
-            }
+                    analyzerConfigOptions.TryGetValue(key, out var optionValue);
+                    return optionValue;
+                });
 
-            public IEnumerable<string> Keys => throw new NotImplementedException();
-
-            public IEnumerable<string> Values => throw new NotImplementedException();
-
-            public int Count => throw new NotImplementedException();
-
-            public bool ContainsKey(string key)
-            {
-                return _analyzerConfigOptions.TryGetValue(key, out _);
-            }
-
-            public IEnumerator<KeyValuePair<string, string>> GetEnumerator()
-            {
-                throw new NotImplementedException();
-            }
-
-            public bool TryGetValue(string key, out string value)
-            {
-                return _analyzerConfigOptions.TryGetValue(key, out value);
-            }
-
-            IEnumerator IEnumerable.GetEnumerator()
-            {
-                throw new NotImplementedException();
-            }
+            return editorConfigStorageLocation.TryGetOption(optionDictionary, type, out value);
         }
     }
 }
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/ProjectState.cs b/src/Workspaces/Core/Portable/Workspace/Solution/ProjectState.cs
index 47d6c23c06e5e0a2fb5c164c8288fe6fb99a29ef..6d4a83147170c4c67988ed35d7d3b0936226c417 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/ProjectState.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/ProjectState.cs
@@ -307,12 +307,18 @@ public override AnalyzerConfigOptions GetOptions(AdditionalText textFile)
             }
 
             // PROTOTYPE: why isn't this just a provided implementation?
-            private sealed class WorkspaceAnalyzerConfigOptions : DictionaryBackedAnalyzerConfigOptions
+            private sealed class WorkspaceAnalyzerConfigOptions : AnalyzerConfigOptions
             {
+                private readonly ImmutableDictionary<string, string> _backing;
+
                 public WorkspaceAnalyzerConfigOptions(AnalyzerConfigOptionsResult analyzerConfigOptions)
-                    : base(analyzerConfigOptions.AnalyzerOptions)
                 {
+                    _backing = analyzerConfigOptions.AnalyzerOptions;
                 }
+
+                public override bool TryGetValue(string key, out string value) => _backing.TryGetValue(key, out value);
+
+                public override ImmutableArray<string> Keys => _backing.Keys.ToImmutableArray();
             }
         }