Fix PR feedback.

src/Avalonia.Base/Utilities/Ref.cs

@@ -57,13 +57,14 @@ namespace Avalonia.Utilities
                 var old = _refs;
                 while (true)
                 {
+                    if (old == 0)
+                    {
+                        throw new ObjectDisposedException("Cannot add a reference to a nonreferenced item");
+                    }
                     var current = Interlocked.CompareExchange(ref _refs, old + 1, old);
                     if (current == old)
                     {
-                        if (current == 0)
-                        {
-                            throw new ObjectDisposedException("Cannot add a reference to a 0-referenced item");
-                        }
+                        break;
                     }
                     old = current;
                 }
@@ -78,12 +79,12 @@ namespace Avalonia.Utilities
 
                     if (current == old)
                     {
-                        if (current == 1)
+                        if (old == 1)
                         {
                             _item.Dispose();
                             _item = null;
                         }
-                        return;
+                        break;
                     }
                     old = current;
                 }
@@ -100,6 +101,7 @@ namespace Avalonia.Utilities
             {
                 _item = item;
                 _counter = counter;
+                Interlocked.MemoryBarrier();
                 _counter.AddRef();
             }
 
@@ -148,9 +150,7 @@ namespace Avalonia.Utilities
                 {
                     if (_item != null)
                     {
-                        TResult castItem = null;
-                        Volatile.Write(ref castItem, (TResult)(object)_item);
-                        return new Ref<TResult>(castItem, _counter);
+                        return new Ref<TResult>((TResult)(object)_item, _counter);
                     }
                     throw new ObjectDisposedException("Ref<" + typeof(T) + ">");
                 }