using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(MillisecondsToDateTime("1549956673944.208252").ToString());

    }

    public static DateTime MillisecondsToDateTime(string _unixTimeStamp)

        {

            double unixTimeStamp = 0;

            double.TryParse(_unixTimeStamp, out unixTimeStamp);

            System.DateTime dtDateTime = new DateTime(1970, 1, 1, 0, 0, 0, 0);

            dtDateTime = dtDateTime.AddMilliseconds(unixTimeStamp).ToLocalTime();

            return dtDateTime;

        }

}