using System;

public class Program

{

    public static void Main()

    {

        DateTime? login = null;

        DateTime? logout = null;

        //Declaring login. Not declaring logout intensionally

        login = new DateTime(2017,1,1);

        //Will return Date and time value

        Console.WriteLine(login.HasValue ? login.Value.ToString("MM/dd/yyyy"): String.Empty);

        //will return nothing as it is returning string.Emtpy

        Console.WriteLine(logout.HasValue ? logout.Value.ToString("MM/DD/YYYY"): String.Empty);

    }

}