C# – How to override List‘s Add method in C#


I am currently looking to make my own collection, which would be just like a regular list, except that it would only hold 10 items. If an item was added when there were already 10 items in the list, then the first item would be removed before the new item was appended.

What I want to do is create a class that extends System.Collections.Generic.List<T>, and then modifies the Add(T item) method to include the functionality which removes the first item if necessary.

Best Solution

You can also implement the add method via

public new void Add(...)

in your derived class to hide the existing add and introduce your functionality.

Edit: Rough Outline...

class MyHappyList<T> : List<T>
    public new void Add(T item)
        if (Count > 9)


Just a note, figured it was implied but you must always reference your custom list by the actual type and never by the base type/interface as the hiding method is only available to your type and further derived types.