.net - C#: Inheritance Problem with List<T>

Question

Let's assume this class in C#:

public class LimitedList<T> : List<T>
{
    private int _maxitems = 500;

    public void Add(T value) /* Adding a new Value to the buffer */
    {
        base.Add(value);
        TrimData(); /* Delete old data if lenght too long */
    }

    private void TrimData()
    {
        int num = Math.Max(0, base.Count - _maxitems);
        base.RemoveRange(0, num);
    }
}

The compiler gives me this warning in the line "public void Add(T value)":

warning CS0108: 'System.LimitedList.Add(T)' hides inherited member 'System.Collections.Generic.List.Add(T)'. Use the new keyword if hiding was intended.

What do I have to do to avoid this warning?

Thx 4 your help

Answer 1

No - don't use new here; that doesn't give you polymorphism. List<T> isn't intended for inheritance in this way; use Collection<T> and override the Add InsertItem method.

public class LimitedCollection<T> : Collection<T>
{
    private int _maxitems = 500;

    protected override void InsertItem(int index, T item)
    {
        base.InsertItem(index, item);
        TrimData(); /* Delete old data if lenght too long */
    }

    private void TrimData()
    {
        int num = Math.Max(0, base.Count - _maxitems);
        while (num > 0)
        {
            base.RemoveAt(0);
            num--;
        }
    }
}