Fix inconsistency with IDE for sorting usings for Windows.* namespaces when system using directives first is enabled

Author: ali-hk

StyleCop.Analyzers/StyleCop.Analyzers.CodeFixes/OrderingRules/UsingCodeFixProvider.UsingsSorter.cs

@@ -438,7 +438,7 @@ private bool IsSeparatedSystemUsing(UsingDirectiveSyntax syntax)
                 var namespaceTypeName = namespaceSymbol.ToDisplayString(FullNamespaceDisplayFormat);
                 var firstPart = namespaceTypeName.Split('.')[0];
 
-                return string.Equals(SystemUsingDirectiveIdentifier, firstPart, StringComparison.Ordinal);
+                return string.Equals(SystemUsingDirectiveIdentifier, firstPart, StringComparison.Ordinal) || string.Equals(WindowsUsingDirectiveIdentifier, firstPart, StringComparison.Ordinal);
             }
 
             private void ProcessMembers(SyntaxList<MemberDeclarationSyntax> members)

StyleCop.Analyzers/StyleCop.Analyzers.CodeFixes/OrderingRules/UsingCodeFixProvider.cs

@@ -26,6 +26,7 @@ namespace StyleCop.Analyzers.OrderingRules
     internal sealed partial class UsingCodeFixProvider : CodeFixProvider
     {
         private const string SystemUsingDirectiveIdentifier = nameof(System);
+        private const string WindowsUsingDirectiveIdentifier = "Windows";
 
         private static readonly List<UsingDirectiveSyntax> EmptyUsingsList = new List<UsingDirectiveSyntax>();
         private static readonly SyntaxAnnotation UsingCodeFixAnnotation = new SyntaxAnnotation(nameof(UsingCodeFixAnnotation));

StyleCop.Analyzers/StyleCop.Analyzers/Helpers/UsingDirectiveSyntaxHelpers.cs

@@ -16,13 +16,20 @@ namespace StyleCop.Analyzers.Helpers
     internal static class UsingDirectiveSyntaxHelpers
     {
         private const string SystemUsingDirectiveIdentifier = nameof(System);
+        private const string WindowsUsingDirectiveIdentifier = "Windows";
 
         /// <summary>
         /// Check if <see cref="UsingDirectiveSyntax"/> is system using directive.
         /// </summary>
         /// <param name="usingDirective">The <see cref="UsingDirectiveSyntax"/> that will be checked.</param>
         /// <returns>Return true if the <see cref="UsingDirectiveSyntax"/>is system using directive, otherwise false.</returns>
-        internal static bool IsSystemUsingDirective(this UsingDirectiveSyntax usingDirective) => string.Equals(SystemUsingDirectiveIdentifier, GetFirstIdentifierInUsingDirective(usingDirective)?.ValueText, StringComparison.Ordinal);
+        internal static bool IsSystemUsingDirective(this UsingDirectiveSyntax usingDirective)
+        {
+            string firstIdentifier = GetFirstIdentifierInUsingDirective(usingDirective)?.ValueText;
+
+            // Visual Studio treats Windows.* namespaces as system namespaces.
+            return string.Equals(SystemUsingDirectiveIdentifier, firstIdentifier, StringComparison.Ordinal) || string.Equals(WindowsUsingDirectiveIdentifier, firstIdentifier, StringComparison.Ordinal);
+        }
 
         /// <summary>
         /// Check if <see cref="UsingDirectiveSyntax"/> is preceded by a preprocessor directive.