Use reference entity comparison

Author: bahusoid

src/NHibernate/Collection/AbstractPersistentCollection.cs

@@ -726,7 +726,7 @@ protected virtual ICollection GetOrphans(ICollection oldElements, ICollection cu
 				return oldElements;
 			}
 
-			if (currentElements.Count == oldElements.Count && currentElements.Cast<object>().SequenceEqual(oldElements.Cast<object>()))
+			if (currentElements.Count == oldElements.Count && currentElements.Cast<object>().SequenceEqual(oldElements.Cast<object>(), ReferenceComparer<object>.Instance))
 				return Array.Empty<object>();
 
 			var persister = session.Factory.GetEntityPersister(entityName);

src/NHibernate/Util/ReferenceComparer.cs

@@ -0,0 +1,40 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+
+namespace NHibernate.Util
+{
+	/// <summary>
+	/// Compares objects by reference equality
+	/// </summary>
+	/// <typeparam name="T"></typeparam>
+	[Serializable]
+	class ReferenceComparer<T> : IEqualityComparer, IEqualityComparer<T> where T : class
+	{
+		private ReferenceComparer()
+		{
+		}
+
+		public bool Equals(T x, T y)
+		{
+			return ReferenceEquals(x, y);
+		}
+
+		public int GetHashCode(T obj)
+		{
+			return System.Runtime.CompilerServices.RuntimeHelpers.GetHashCode(obj);
+		}
+
+		bool IEqualityComparer.Equals(object x, object y)
+		{
+			return ReferenceEquals(x, y);
+		}
+
+		int IEqualityComparer.GetHashCode(object obj)
+		{
+			return System.Runtime.CompilerServices.RuntimeHelpers.GetHashCode(obj);
+		}
+
+		public static readonly ReferenceComparer<T> Instance = new ReferenceComparer<T>();
+	}
+}