using System.Collections.Generic;

​

public sealed class PatternSample

{

    private static PatternSample instance = null;

    private List<string> items = new List<string>();

    PatternSample()

    {

    }

​

    public static PatternSample Instance

    {

        get

        {

            if (instance == null)

            {

                instance = new PatternSample();

            }

​

            return instance;

        }

    }

    public void AddItem(string item)

    {

        this.items.Add(item);

    }

}