using System;

​

public static class StaticParameters

{

    public static string ToShortDate(DateTime? date)

        {

            if (date == null || !date.HasValue) return "";

​

​

            return date.Value.ToShortDateString();

        }

}

​

public static class DateTimeExtensions

{

    public static string ToShortDate(this DateTime? date)

        {

            if (date == null || !date.HasValue) { return ""; }

​

​

            return date.Value.ToShortDateString();

        }

}

​

public static class Format

{

    public static string FormatWithArgOrEmpty(string s, string arg0)

    {

        if (string.IsNullOrEmpty(s) || string.IsNullOrEmpty(arg0)) return "";

​

        return string.Format(s, arg0);

    }

}

​

public class Program

{

    public static void Main()

    {

        DateTime? NextDate = null;

        string nextDate_Un = Format.FormatWithArgOrEmpty("Prochain départ le {0}", StaticParameters.ToShortDate(NextDate));

        string nextDate_Deux = Format.FormatWithArgOrEmpty("Prochain départ le {0}", NextDate.ToShortDate());

        Console.WriteLine("Début");

        Console.WriteLine(nextDate_Un);

        Console.WriteLine(nextDate_Deux);

        Console.WriteLine("Fin");

    }

}