using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var test = new List<Test>(){

            new Test(null), new Test(new DateTime())

        };

        test = test.OrderByDescending(fr => fr.date).ToList();

        Console.Write(test.First().date);

    }

}

​

public class Test{

    public Test( DateTime? val){

        date = val;

    }

    public DateTime? date {get;set;}

}