Update StyleCop.Analyzers/StyleCop.Analyzers/OrderingRules/SA1201ElementsMustAppearInTheCorrectOrder.cs

Co-authored-by: Sam Harwell <sam@tunnelvisionlabs.com>

Author: vweijsters

StyleCop.Analyzers/StyleCop.Analyzers/Helpers/DictionaryExtensions.cs

@@ -0,0 +1,21 @@
+// Copyright (c) Tunnel Vision Laboratories, LLC. All Rights Reserved.
+// Licensed under the MIT License. See LICENSE in the project root for license information.
+
+namespace StyleCop.Analyzers.Helpers
+{
+    using System.Collections.Generic;
+
+    internal static class DictionaryExtensions
+    {
+        public static TValue GetValueOrDefault<TKey, TValue>(this Dictionary<TKey, TValue> dictionary, TKey key, TValue defaultValue)
+          where TKey : notnull
+        {
+            if (!dictionary.TryGetValue(key, out var value))
+            {
+                value = defaultValue;
+            }
+
+            return value;
+        }
+    }
+}

StyleCop.Analyzers/StyleCop.Analyzers/OrderingRules/SA1201ElementsMustAppearInTheCorrectOrder.cs

@@ -297,8 +297,8 @@ private static void HandleMemberList(SyntaxNodeAnalysisContext context, Immutabl
                 if (index > nextIndex)
                 {
                     // [Issue #3160] Added hardening here to make sure that this won't crash when working with invalid code.
-                    var nextElementMemberName = MemberNames.ContainsKey(nextElementSyntaxKind) ? MemberNames[nextElementSyntaxKind] : "<unknown>";
-                    var elementMemberName = MemberNames.ContainsKey(elementSyntaxKind) ? MemberNames[elementSyntaxKind] : "<unknown>";
+                    var nextElementMemberName = MemberNames.GetValueOrDefault(nextElementSyntaxKind, "<unknown>");
+                    var elementMemberName = MemberNames.GetValueOrDefault(elementSyntaxKind, "<unknown>");
 
                     context.ReportDiagnostic(Diagnostic.Create(Descriptor, NamedTypeHelpers.GetNameOrIdentifierLocation(members[i + 1]), nextElementMemberName, elementMemberName));
                 }