using System;

public class Program

{

    public static void Main()

    {

        string input = "24.04.2018 00:00:00";

​

        DateTime d;

        if (DateTime.TryParseExact(input, "dd.MM.yyyy HH:mm:ss", System.Globalization.CultureInfo.InvariantCulture, System.Globalization.DateTimeStyles.None, out d))

        {

            Console.WriteLine(d.ToString("MM/dd/yyyy"));

        }

    }

}