https://learn.microsoft.com/ru-ru/dotnet/api/system.windows.markup.contentwrapperattribute?view=netframework-4.8.1&viewFallbackFrom=net-10.0
ContentWrapperAttribute Class (System.Windows.Markup) | Microsoft Learn
Specifies one or more types on the associated collection type that will be used to wrap foreign content.
class systemwindowsmarkupmicrosoftlearn