Convert portion of string to datetime in C#

Question

I have two parameters defined in appsettings.json of an asp.net core project.

  "TimeParam": {
    "StartTime": "00:00:00.0001",
    "EndTime": "23:59:99.999"
    "BackOffDay": 1
  },

In a function, I need to pass two parameters as startDate and endDate of data type date.

For example, for the startDate I need to be like 17/06/2020 00:00:00.0001 and the endDate to be like 17/06/2020 23:59:99.999

How can I get to set the two variable as follows taking into consideration the time that I have set in the appsettings.json?

StartDate: DateTime.Now.AddDays(BackOffDay) EndDate: DateTime.Now

var startDate = DateTime.Parse($"{DateTime.Now.AddDays(BackOffDay):dd/MM/yyyy} {StartTime}"); and similarly for endDate. — itsme86
– itsme86, Commented Jun 18, 2020 at 17:33
System.FormatException: String was not recognized as a valid DateTime. — CadaMerx
– CadaMerx, Commented Jun 18, 2020 at 17:36
Is your culture set for day/month/year? If not, you can use ParseExact() instead. — itsme86
– itsme86, Commented Jun 18, 2020 at 17:39

Community · Accepted Answer · 2020-06-20 09:12:55Z

4

You tricked me a second there, 23:59:99.999 is no parseable time as there are only 59 seconds in a minute.

But here you go:

using System;           
using System.Globalization;
public class Program
{
    public static void Main()
    {
        var start= "00:00:00.0001";
        var end = "23:59:59.999";
        int backOffDay = 1;
        
        var startTimeSpan = TimeSpan.Parse(start);
        var endTimeSpan = TimeSpan.Parse(end);
        
        var startTime = DateTime.Now.Date.AddDays(backOffDay).Add(startTimeSpan);
        var endTime = DateTime.Now.Date.AddDays(backOffDay).Add(endTimeSpan);
        
        Console.WriteLine(startTime.ToString("dd/MM/yyyy H:mm:ss.FFFF"));
        Console.WriteLine(endTime.ToString("dd/MM/yyyy H:mm:ss.FFFF"));
    }
}

You can test it with this fiddle.

19/06/2020 0:00:00.0001

19/06/2020 23:59:59.999

P.S.: To make sure all timestamps are always parsed the same, you might want to do something like this as well:

CultureInfo.DefaultThreadCurrentCulture = new CultureInfo("en-US");

or just for a single call:

var culture = new CultureInfo("en-US");
var startTimeSpan = TimeSpan.Parse(start, culture);

Although parsing seemed to work well with en-US culture I wouldn't guarantee it does in all enivronments.

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Jun 18, 2020 at 17:41

Vivien Sonntag

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2 Comments

CadaMerx Over a year ago

Thanks for this beautiful answer!. Is var end = "23:59:59.9999"; or it should only contain three 999 correct ?

Vivien Sonntag Over a year ago

You're welcome - I updated my answer and the fiddle to use ".FFFF" instead of ".ffff". This will omit trailing zeros. P.S.: You didn't clearly specify "backOffDate", if you want it to be one day ago just use -1 * backOffDay instead of backOffDay.

JonasH · Accepted Answer · 2020-06-18 17:39:48Z

2

Use DateTime.Now.Date, then add the start and end time to create the start date and end date respectively. Use TimeSpan.Parse to parse the times.

(DateTime.Now.Date + TimeSpan.Parse("13:01:05")).ToString();
//2020-06-18 13:01:05

edited Jun 18, 2020 at 17:39

answered Jun 18, 2020 at 17:31

JonasH

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4 Comments

CadaMerx Over a year ago

I need to concatenate the date and time together. And then obtain the datetime as 17/06/2020 00:00:00.0001

JonasH Over a year ago

@CadaMerx Adding the date-portion of a DateTime and a timespan does exactly that.

CadaMerx Over a year ago

An example please ?

Jacob Huckins Over a year ago

@CadaMerx just do what JonasH suggested, then either print the date time or debug and inspect it's value. It will have the times you want on the current date.

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