Simplify UniqueMarshalling native export using StrategyBasedComWrappers

Removed custom MyComWrapper implementation and ImplementingObject class. Now using StrategyBasedComWrappers directly with SharedTypes.ComInterfaces.UniqueMarshalling instance, which leverages the GeneratedComClass attribute to handle the COM vtable automatically.

Co-authored-by: jtschuster <36744439+jtschuster@users.noreply.github.com>

Author: Copilot

src/libraries/System.Runtime.InteropServices/tests/TestAssets/NativeExports/ComInterfaceGenerator/UniqueMarshalling.cs

@@ -1,12 +1,9 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System;
-using System.Collections;
-using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
+using System.Runtime.InteropServices.Marshalling;
 using SharedTypes.ComInterfaces;
-using static System.Runtime.InteropServices.ComWrappers;
 
 namespace NativeExports.ComInterfaceGenerator
 {
@@ -16,117 +13,11 @@ public static unsafe class UniqueMarshalling
         [UnmanagedCallersOnly(EntryPoint = "new_unique_marshalling")]
         public static void* CreateComObject()
         {
-            MyComWrapper cw = new();
-            var myObject = new ImplementingObject();
-            nint ptr = cw.GetOrCreateComInterfaceForObject(myObject, CreateComInterfaceFlags.None);
+            StrategyBasedComWrappers wrappers = new();
+            var myObject = new SharedTypes.ComInterfaces.UniqueMarshalling();
+            nint ptr = wrappers.GetOrCreateComInterfaceForObject(myObject, CreateComInterfaceFlags.None);
 
             return (void*)ptr;
         }
-
-        class MyComWrapper : ComWrappers
-        {
-            static void* _s_comInterface1VTable = null;
-            static void* s_comInterface1VTable
-            {
-                get
-                {
-                    if (MyComWrapper._s_comInterface1VTable != null)
-                        return _s_comInterface1VTable;
-                    void** vtable = (void**)RuntimeHelpers.AllocateTypeAssociatedMemory(typeof(UniqueMarshalling), sizeof(void*) * 6);
-                    GetIUnknownImpl(out var fpQueryInterface, out var fpAddReference, out var fpRelease);
-                    vtable[0] = (void*)fpQueryInterface;
-                    vtable[1] = (void*)fpAddReference;
-                    vtable[2] = (void*)fpRelease;
-                    vtable[3] = (delegate* unmanaged<void*, int*, int>)&ImplementingObject.ABI.GetValue;
-                    vtable[4] = (delegate* unmanaged<void*, int, int>)&ImplementingObject.ABI.SetValue;
-                    vtable[5] = (delegate* unmanaged<void*, void**, int>)&ImplementingObject.ABI.GetThis;
-                    _s_comInterface1VTable = vtable;
-                    return _s_comInterface1VTable;
-                }
-            }
-            protected override ComInterfaceEntry* ComputeVtables(object obj, CreateComInterfaceFlags flags, out int count)
-            {
-                if (obj is ImplementingObject)
-                {
-                    ComInterfaceEntry* comInterfaceEntry = (ComInterfaceEntry*)RuntimeHelpers.AllocateTypeAssociatedMemory(typeof(ImplementingObject), sizeof(ComInterfaceEntry));
-                    comInterfaceEntry->IID = new Guid(IUniqueMarshalling.IID);
-                    comInterfaceEntry->Vtable = (nint)s_comInterface1VTable;
-                    count = 1;
-                    return comInterfaceEntry;
-                }
-                count = 0;
-                return null;
-            }
-
-            protected override object? CreateObject(nint externalComObject, CreateObjectFlags flags) => throw new NotImplementedException();
-            protected override void ReleaseObjects(IEnumerable objects) => throw new NotImplementedException();
-        }
-
-        class ImplementingObject : IUniqueMarshalling
-        {
-            int _data = 0;
-
-            int IUniqueMarshalling.GetValue()
-            {
-                return _data;
-            }
-            void IUniqueMarshalling.SetValue(int x)
-            {
-                _data = x;
-            }
-            IUniqueMarshalling IUniqueMarshalling.GetThis()
-            {
-                return this;
-            }
-
-            // Provides function pointers in the COM format to use in COM VTables
-            public static class ABI
-            {
-
-                [UnmanagedCallersOnly]
-                public static int GetValue(void* @this, int* value)
-                {
-                    try
-                    {
-                        *value = ComInterfaceDispatch.GetInstance<IUniqueMarshalling>((ComInterfaceDispatch*)@this).GetValue();
-                        return 0;
-                    }
-                    catch (Exception e)
-                    {
-                        return e.HResult;
-                    }
-                }
-
-                [UnmanagedCallersOnly]
-                public static int SetValue(void* @this, int newValue)
-                {
-                    try
-                    {
-                        ComInterfaceDispatch.GetInstance<IUniqueMarshalling>((ComInterfaceDispatch*)@this).SetValue(newValue);
-                        return 0;
-                    }
-                    catch (Exception e)
-                    {
-                        return e.HResult;
-                    }
-                }
-
-                [UnmanagedCallersOnly]
-                public static int GetThis(void* @this, void** value)
-                {
-                    try
-                    {
-                        IUniqueMarshalling result = ComInterfaceDispatch.GetInstance<IUniqueMarshalling>((ComInterfaceDispatch*)@this).GetThis();
-                        MyComWrapper cw = new();
-                        *value = (void*)cw.GetOrCreateComInterfaceForObject(result, CreateComInterfaceFlags.None);
-                        return 0;
-                    }
-                    catch (Exception e)
-                    {
-                        return e.HResult;
-                    }
-                }
-            }
-        }
     }
 }