Reintroduce StructLayout attribute on SortKey class

src/libraries/System.DirectoryServices.Protocols/src/System/DirectoryServices/Protocols/Interop/SortKeyInterop.cs

@@ -13,6 +13,7 @@ namespace System.DirectoryServices.Protocols
 {
     // Declared as partial in order to be able to set the different StructLayout
     // attributes in the Windows and Linux specific files.
+    // This is a layout-controlled struct, do not alter property ordering.
     internal partial struct SortKeyInterop
     {
         public SortKeyInterop(SortKey sortKey)
@@ -25,10 +26,10 @@ public SortKeyInterop(SortKey sortKey)
             ReverseOrder = sortKey.ReverseOrder;
         }
 
-        public string AttributeName { get; set; }
+        internal string AttributeName { get; set; }
 
-        public string MatchingRule { get; set; }
+        internal string MatchingRule { get; set; }
 
-        public bool ReverseOrder { get; set; }
+        internal bool ReverseOrder { get; set; }
     }
 }

src/libraries/System.DirectoryServices.Protocols/src/System/DirectoryServices/Protocols/common/DirectoryControl.cs

@@ -50,6 +50,7 @@ internal static class UtilityHandle
         public static ConnectionHandle GetHandle() => s_handle;
     }
 
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
     public class SortKey
     {
         private string _name;