I have an application that has a concept of a Venue, a place where events happen. A Venue is owned by a Company and has many VenueParts. So, it looks like this:

public abstract class Venue
{
    public int Id { get; set; }
    public string Name { get; set; }
    public virtual Company Company { get; set; }
    public virtual ICollection<VenuePart> VenueParts { get; set; }
}

A Venue can be a GolfCourseVenue, which is a Venue that has a Slope and a specific kind of VenuePart called a HoleVenuePart:

public class GolfCourseVenue
{
    public string Slope { get; set; }
    public virtual ICollection<HoleVenuePart> Holes { get; set; }
}

In the future, there may also be other kinds of Venues that all inherit from Venue. They might add their own fields, and will always have VenueParts of their own specific type.

My declarations above seem wrong, because now I have a GolfCourseVenue with two collections, when really it should just have the one. I can't override it, because the type is different, right? When I run reports, I would like to refer to the classes generically, where I just spit out Venues and VenueParts. But, when I render forms and such, I would like to be specific.

I have a lot of relationships like this and am wondering what I am doing wrong. For example, I have an Order that has OrderItems, but also specific kinds of Orders that have specific kinds of OrderItems.