模型构建ASP.NET EntityFramework循环错误

I have these two entities:

我有这两个实体:

public class Contact : PrimaryKey
{
    public ICollection<Order> OrdersPlaced {get;set;}
}

public class Order : PrimaryKey
{
    public Contact OrderedBy {get;set;}
    public Guid OrderedById {get;set;}
}
public