How to expose a collection property? [closed]

Answer 1

I recommend to use the new IReadOnlyList and IReadOnlyCollection Interfaces to expose a collection (requires .NET 4.5).

Example:

public class AddressBook
{
    private readonly List contacts;

    public AddressBook()
    {
        this.contacts = new List();
    }

    public IReadOnlyList Contacts { get { return contacts; } }

    public void AddContact(Contact contact)
    {
        contacts.Add(contact);
    }

    public void RemoveContact(Contact contact)
    {
        contacts.Remove(contact);
    }
}

If you need to guarantee that the collection can not be manipulated from outside then consider ReadOnlyCollection or the new Immutable collections.

Avoid using the interface IEnumerable to expose a collection. This interface does not define any guarantee that multiple enumerations perform well. If the IEnumerable represents a query then every enumeration execute the query again. Developers that get an instance of IEnumerable do not know if it represents a collection or a query.

More about this topic can be read on this Wiki page.