using System;

​

public abstract class Plugin<T> where T : new()

{

    private static readonly Lazy<T> val = new Lazy<T>(() => new T());

    public static T Instance { get { return val.Value; } }

​

    protected Plugin() { }

​

    public abstract string plugin_name();

}

​

public class Main : Plugin<Main> {

    public override string plugin_name() { return "a test plugin"; }

}

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine(global::Main.Instance.plugin_name());

    }

}