The only field in Person that is shared with all of the decedents is the field 'name', therefore, if you are casting each item in your list to Person you will only have access to 'name'.
You have a few options to solve this issue. 1) you could move all of the common fields into the base class, but this is probably not want since it defeats the point of an object hierarchy, or 2) you can type check, using the "Is" keyword, each person in the list so see what type of person it is and then cast that Person to the appropriate decedent class before you operate on it.
For example:
foreach (Person p in list.People)
{
if(p is Employee)
{
Debug.WriteLine(((Employee)p).salary.toString());
}
if(p is Guest)
{
Debug.WriteLine(((Guest)p).Id.toString());
}
}
Here is an alternate more clear way of casting
foreach (Person p in list.People)
{
if(p is Employee)
{
Employee employee = p as Employee;
Debug.WriteLine(employee.salary.toString());
}
if(p is Guest)
{
Guest guest = p as Guest;
Debug.WriteLine(guest.Id.toString());
}
}
Additionally you can learn more about type checking using the "is" keyword here.
Also just for clarity, since it might not be obvious, some others have suggested that you use OfType in linq but this more of a way to filter like object from a list of mixed objects as opposed to actually type checking each one.
Enjoy!