Use generic arguments if possible to get type of elements in lists

Author: lhak

components/Collections/src/AdvancedCollectionView/AdvancedCollectionView.cs

@@ -382,7 +382,18 @@ int IComparer<object>.Compare(object x, object y)
     {
         if (!_sortProperties.Any())
         {
-            var type = x.GetType();
+            var listType = _source?.GetType();
+            Type type;
+
+            if (listType != null && listType.IsGenericType)
+            {
+                type = listType.GetGenericArguments()[0];
+            }
+            else
+            {
+                type = x.GetType();
+            }
+
             foreach (var sd in _sortDescriptions)
             {
                 if (!string.IsNullOrEmpty(sd.PropertyName))