using System.Collections;

namespace System.Windows.Forms
{
    public partial class ListBox
    {
        public class SelectedIndexCollection : CollectionBase
        {
            private ListBox owner;

            public int this[int index] => (int)List[index];

            public void Add(int index)
            {
                owner.SelectedItems.Add(owner.Items[index]);
            }

            public void AddInternal(int index)
            {
                List.Add(index);
            }

            public void Remove(int index)
            {
                owner.SelectedItems.Remove(owner.Items[index]);
            }

            public new void Clear()
            {
                owner.SelectedItems.Clear();
            }

            public int IndexOf(int selectedIndex) => List.IndexOf(selectedIndex);

            public bool Contains(int selectedIndex) => IndexOf(selectedIndex) != -1;


            internal SelectedIndexCollection(ListBox owner) => this.owner = owner;
        }
    }
}