Why is the type of the parent class property not defined?

Question

.NET

Hello.
in a project under C++/CLI I inherit from a class defined in C# code and the development environment does not determine the property type from the parent class. Yes, such a thing can be if you do not register using namespace, but it seems to have registered everything and the IEnumerable ^ type if you make the variable visible, but the property from the parent does not. What to do?