using System;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        List<string> list = null;

        Console.WriteLine(list.IsNullOrEmpty());

        list = new();

        Console.WriteLine(list.IsNullOrEmpty());

        list.Add("");

        Console.WriteLine(list.IsNullOrEmpty());

    }

}

​

public static class ListExtensions

{

    public static bool IsNullOrEmpty<T>(this List<T> list)

       => list is null || list.Count == 0;

}