using System;

using System.Globalization;

​

public class Program

{

    public static void Main(string[] args)

    {

        var dataopen = "9.28.17 13:35";

        DateTime dateTime2;

        if (DateTime.TryParse(dataopen, DateTimeFormatInfo.InvariantInfo, DateTimeStyles.None, out dateTime2))

        {

            Console.WriteLine(dateTime2);

        }

    }

}