Develop Reference

DateTime Resets at midnight

Hi I am using C# web app on visual studio.
I have written code to be able to distinguish if the time is between 6am-2pm - 2pm-10pm and 10pm - 6am...
The code runs like a dream for the 6-2 - 2-10 times but for the 10pm - 6am.. the code runs fine until midnight and then it just resets my counter to 0 and stays at 0 until 6am.. I can't get my head around why this is doing.. Does anybody have a solution..
public DateTime Shiftstart { get; set; }
public DateTime Shiftend { get; set; }
public string Itemseriesmaster { get; set; }
public string SeriesMasterId { get; set; }
public void CalcShiftPeriod() //constructor
{
DateTime now = DateTime.Now; //date time now
int currentHour = now.Hour; //hour now
int shiftHourStart;
if (currentHour >= 6 && currentHour <= 13)
{
shiftHourStart = 6;
}
else if (currentHour >= 14 && currentHour <= 21)
{
shiftHourStart = 14;
}
else
{
shiftHourStart = 22;
}
Shiftstart = now.Date.AddHours(shiftHourStart);
Shiftend = Shiftstart.AddHours(7);
Shiftend = Shiftend.AddMinutes(59);
Shiftend = Shiftend.AddSeconds(59);
}
The code is calculating total units packed and is working fine, and resets after the given time on both the 6-2 and 2 - 10 shifts..
Until it gets to the 10pm - 6am and then just completely stops at midnight.
BizManager biz = new BizManager();
DataTable dt = new DataTable();
if (DDLProduct.SelectedValue.Equals("G120C-2") || DDLProduct.SelectedValue.Equals("G120 PM240-2") )
{
RefreshMainGridTht(selectedProduct, shiftStart, shiftEnd
);
}
dt = biz.GetPacktstatisticsForShift(shiftStart, shiftEnd, selectedProduct);
GridView1.DataSource = dt.DefaultView;
GridView1.DataBind();
int sumActual = 0;
int sumTarget = 0;
biz.CalculatePackingTotals(dt, out sumActual, out sumTarget);
LabelTotal.Text = sumActual.ToString();
DateTime dtmNow = DateTime.Now;
TimeSpan tsIntoShift = dtmNow - shiftStart;
TimeSpan tsTotalShift = shiftEnd - shiftStart;
double p = tsIntoShift.TotalMinutes / tsTotalShift.TotalMinutes;
int adjustedTarget = Convert.ToInt32(sumTarget * p);
if (sumActual > sumTarget)
{
LabelTotal.ForeColor = Color.Lime;
}
else
{
LabelTotal.ForeColor = Color.Red;
}
}
catch (Exception ex)
{
ErrMsg = App.HandleError(MethodBase.GetCurrentMethod(), ex, string.Empty);

You have to distinguish between currentHour from 0 to 5 and currentHour from 22 to 23.
For example, consider currentHour is 1. Your calculation says that the shift starts at 22:00 of the current day (now.Date.AddHours(22)), which is obviously wrong because the shift already started at 22:00 of the previous day.
So from currentHour 0 to 5 you have to subtract a day from your Shiftstart.
One possible way to do that would be to set shiftHourStart to -2 for currentHour between 0 and 5.
if (currentHour < 6)
{
shiftHourStart = -2;
}
else if (currentHour >= 6 && currentHour <= 13)
{
shiftHourStart = 6;
}
else if (currentHour >= 14 && currentHour <= 21)
{
shiftHourStart = 14;
}
else
{
shiftHourStart = 22;
}

The error lies in adding the hours to the current day...
Shiftstart = now.Date.AddHours(shiftHourStart);
At 23:59 you are adding 22 hours to "2018-11-06".
One minute passes...
At 00:00 you are adding 22 hours to "2018-11-07".
That means your start time moves 24 hours over the course of that one minute.
You could distinguish this scenario as part of your if-statement. See the comments a) and b) below.
int currentHour = now.Hour;
DateTime date = now.Date; // a) This is today in most cases...
int shiftHourStart;
if (currentHour >= 6 && currentHour <= 13)
{
shiftHourStart = 6;
}
else if (currentHour >= 14 && currentHour <= 21)
{
shiftHourStart = 14;
}
else if (currentHour >= 22)
{
shiftHourStart = 22;
}
else
{
// midnight to 6am
date = date.AddDays(-1); // b) But not in this case
shiftHourStart = 22;
}

First store your time in a TimeSpan this will give you more flexibility if tomorrow shift start and ends at 30min. Then store those Timespan in a class that represent the time frame. And if you have a list of them make it a List. It will help reading and maintaining your code. For now it's a brunch of magic numbers.
To check if a time is in a Range, I used :
public static bool IsBetween(TimeSpan time, TimeSpan start, TimeSpan end)
=> (start <= end) ? time >= start && time <= end : time >= start || time <= end;
internal void TestMethod()
{
var timeSlots = new[] {
new TimeFrame { start= new TimeSpan(6,0,0) , end = new TimeSpan(13,0,0) },
new TimeFrame { start= new TimeSpan(14,0,0) , end = new TimeSpan(21,0,0) },
new TimeFrame { start= new TimeSpan(22,0,0) , end = new TimeSpan(6,0,0) }
};
var today = DateTime.Today;
var dayHours = Enumerable.Range(0, 24).Select(x => today.AddHours(x)).ToList();
foreach (var currentDateTime in dayHours)
{
var matchingRanges = timeSlots.Where(x => IsBetween(currentDateTime .TimeOfDay, x.start, x.end));
if (matchingRanges.Any())
{
var temp = matchingRanges.First();
Console.WriteLine($"-> {currentDateTime } is in range {temp.start}-{temp.end}");
Console.WriteLine($"\t ShiftHours= {temp.start}-{temp.end.Subtract(new TimeSpan(0, 0, 1))}");
}
else
{
Console.WriteLine($"no Match for {currentDateTime }");
}
}
}
As you added a comment about testing it at midnight , included a TestMethod where I create all hours of a day (from 00h to 23h) so you can easly see what going on.

c# date methods not working

I have created a Date program which should return the user the date when inputted. I have not been using DateTime, as I wanted to create my own Date class instead. For some reason within my if statements my value does not seem to be working within my main for some reason. Is there any way around this problem?
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace date
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine("please enter date as dd/MM/yyyy");
int day;
int month;
int year;
string[] read = Console.ReadLine().Split('/');
day = int.Parse(read[0]);
month = int.Parse(read[1]);
year = int.Parse(read[2]);
Date i = new Date(day, month, year);
Console.WriteLine("{0}/{1}/{2}", i.day, i.month, i.year);
Console.ReadLine();
}
class Date
{
public int month; // 1-12
public int day; // 1-31 depending on month
public int year
{
get;
private set;
}
public Date(int day, int month, int year)
{
this.day = day;
this.month = month;
this.year = year;
}
public int Year
{
get { return year; }
set
{
if (value > 0 && value <= 12)
month = value;
else
throw new ArgumentOutOfRangeException("year", value, "year out of range");
}
}
private int Month
{
get { return month; }
set
{
if (value > 0 && value <= 12)
month = value;
else
throw new ArgumentOutOfRangeException("Month", value, "Month must be 1-12");
}
}
public int Day
{
get { return day; }
set
{
int[] days = { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
if (value > 0 && value <= days[month])
day = value;
else if (month == 2 && value == 29 &&
year % 400 == 0 || (year % 4 == 0 && year % 100 != 0))
day = value;
else
throw new ArgumentOutOfRangeException("days", value, "day is out of range");
}
}
}
}
}

You are using member variables, not properties as you intended
Console.WriteLine("{0}/{1}/{2}", i.Day, i.Month, i.Year);
changed the .day to .Day
Refactored your code a little bit. This way, it will do all the validations when you try setting the values. Setters can be made private, as you might only allow the user to set thing via constructor.
class Date
{
private int _month; // 1-12
private int _day; // 1-31 depending on month
private int _year;
public Date(int day, int month, int year)
{
Day = day;
Month = month;
Year = year;
}
public int Year
{
get { return _year; }
set
{
_year = value;
//Do you checks and throw exception as needed
//throw new ArgumentOutOfRangeException("year", value, "year out of range");
}
}
public int Month
{
get { return _month; }
set
{
if (value > 0 && value <= 12)
_month = value;
else
throw new ArgumentOutOfRangeException("Month", value, "Month must be 1-12");
}
}
public int Day
{
get { return _day; }
set
{
int[] days = { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
if (value > 0 && value <= days[_month])
_day = value;
else if (_month == 2 && value == 29 &&
_year % 400 == 0 || (_year % 4 == 0 && _year % 100 != 0))
_day = value;
else
throw new ArgumentOutOfRangeException("Day", value, "Day is out of range");
}
}
}

I don't have reputation enough to comment. So I answer: Lacked the leap year in your date class.

Besides learning a new language there is no reason in C# to reinvent new Date classes.
It is one of the biggest mistakes coming from the C++ ages before an official string type was there. Everybody had its own string class. We have now about 6 in our software with code to convert between all of them.
So my advise: Don't do this and instead try to read the documentation because most of the functionality is there. If it isn't there, please create extension methods and at last resort derive oder embed the existing class.

c# out of range errors

I have created my own DateTime class and it seems to be working. I was just wondering how can I print errors within my console for my ArgumentOutOfRangeExceptions? I am unsure how to do this so I would like some help.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace date
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine("\t\t\t\t\t\tNextDate Application\n\t\t\t\t\t-------------------------------------");
Console.WriteLine("please enter date as dd/MM/yyyy");
int day;
int month;
int year;
string[] read = Console.ReadLine().Split('/');
day = int.Parse(read[0]);
month = int.Parse(read[1]);
year = int.Parse(read[2]);
Date date = new Date(day, month, year);
Console.WriteLine("{0}/{1}/{2}", date.Day, date.Month, date.Year);
Console.ReadLine();
}
class Date
{
private int _month; // 1-12
private int _day; // 1-31 depending on month
private int _year;
public Date(int day, int month, int year)
{
Month = month;
Day = day;
Year = year;
}
public int Year
{
get { return _year; }
set
{
if (value >= 1820 && value <= 2020)
_year = value;
else
throw new ArgumentOutOfRangeException("year", value, "year out of range");
}
}
public int Month
{
get { return _month; }
set
{
if (value > 0 && value <= 12)
_month = value;
else
throw new ArgumentOutOfRangeException("Month", value, "Month must be 1-12");
}
}
public int Day
{
get { return _day; }
set
{
int[] days = { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
if (value > 0 && value <= days[_month])
_day = value;
else if (_month == 2 && value == 29 &&
_year % 400 == 0 || (_year % 4 == 0 && _year % 100 != 0))
_day = value;
else
throw new ArgumentOutOfRangeException("Day", value, "Day is out of range");
}
}
}
}
}

simply catch the exceptions you throw
try
{
Date date = new Date(day, month, year);
}
catch(ArgumentOutOfRangeException exc)
{
Console.WriteLine(exc.Message);
}
also note that you have to handle user input: you are assuming that he will insert a string such "NN/NN/NNNN". What if he insert "NN/NN"? or "this/will/crash"?

Given your current design, you could do it like this:
try
{
Date date = new Date(day, month, year);
Console.WriteLine("{0}/{1}/{2}", date.Day, date.Month, date.Year);
}
catch (ArgumentOutOfRangeException ex)
{
Console.WriteLine(ex.Message);
}
Note that reinventing the wheel isn't necessary (unless you're intentionally experimenting)... using the correct built-in .NET constructs (like TryParseExact instead of throwing and catching exceptions) will save you a lot of trouble:
Console.WriteLine("please enter date as dd/MM/yyyy");
DateTime date;
if (DateTime.TryParseExact(Console.ReadLine(), "dd/MM/yyyy", null, DateTimeStyles.None, out date))
{
Console.WriteLine("Correct date: {0}", date.ToString("dd/MM/yyyy"));
}
else
{
Console.WriteLine("Invalid date!");
}
Console.ReadLine();

Check if a datetime is in same week as other datetime

Let's say I have a list of dates in a table. Now I want to find all rows, which is in the same week as the date provided as an argument.
Let's say I have a table with:
2014-09-11
2014-09-12
2014-09-15
And I give this function the argument 2014-09-09, it has to look from monday->sunday, and realize that 09-11 and 09-12 is part of the week, but not 09-15.
How on earth to solve this?
I have thought on making a check on year, month and weeknumber, but you cannot guarantee that month is the same...
So how do you solve a problem like this?

DxCk's comment is valid. This solution will work even if the first or last week of the year cross two different years:
Check that the first day of the week for both dates fall on the same day.
Here is the code:
private bool DatesAreInTheSameWeek(DateTime date1, DateTime date2)
{
var cal = System.Globalization.DateTimeFormatInfo.CurrentInfo.Calendar;
var d1 = date1.Date.AddDays(-1 * (int)cal.GetDayOfWeek(date1));
var d2 = date2.Date.AddDays(-1 * (int)cal.GetDayOfWeek(date2));
return d1 == d2;
}

why not?
bool AreFallingInSameWeek(DateTime date1, DateTime date2)
{
return date1.AddDays(-(int)date1.DayOfWeek) == date2.AddDays(-(int)date2.DayOfWeek);
}
if you want to use any day other than Sunday as start of the week
bool AreFallingInSameWeek(DateTime date1, DateTime date2, DayOfWeek weekStartsOn)
{
return date1.AddDays(-GetOffsetedDayofWeek(date1.DayOfWeek, (int)weekStartsOn)) == date2.AddDays(-GetOffsetedDayofWeek(date2.DayOfWeek, (int)weekStartsOn));
}
int GetOffsetedDayofWeek(DayOfWeek dayOfWeek, int offsetBy)
{
return (((int)dayOfWeek - offsetBy + 7) % 7)
}

Check the DateTime.Year and Calendar.GetWeekOfYear(DateTime, ...). No need to check for the month.
EDIT: This is wrong but I can't delete it. See #Sparrow's answer below.

Use: public virtual int GetWeekOfYear(DateTime time,CalendarWeekRule rule,DayOfWeek firstDayOfWeek) of Calendar class

My requirement was to find DOBs falling on the current week. Hope this helps with your doubt. Basically the idea behind this code is as follows:
Change the DOB to current year birthday (eg; 24-02-1988 to 24-02-2018(current year).
Add a year, if the brithday week contains both dec and jan
Get the first day of today's week.
Get last day of today's week.
check if the current year birthday falls between first day and last day of today's week.
private bool DatesAreInTheSameWeek(DateTime birthday)
{
if (birthday == DateTime.MinValue)
{
return false;
}
else
{
var birtdayWithCurrentYear = new DateTime(DateTime.Today.Year, birthday.Month, birthday.Day);
if (birthday.Month == 1 && DateTime.Today.Month != 1)
{
birtdayWithCurrentYear = birtdayWithCurrentYear.AddYears(1);
}
DateTime firstDayInWeek = DateTime.Today.Date;
while (firstDayInWeek.DayOfWeek != CultureInfo.CurrentCulture.DateTimeFormat.FirstDayOfWeek)
firstDayInWeek = firstDayInWeek.AddDays(-1);var lastDayInWeek = firstDayInWeek.AddDays(7);
return birtdayWithCurrentYear < lastDayInWeek && birtdayWithCurrentYear >= firstDayInWeek;
}
}

Since the accepted answer contains error as #DxCK mentioned in comment, here is my solution for this:
public static class DateExtensions
{
private static void Swap<T>(ref T one, ref T two)
{
var temp = one;
one = two;
two = temp;
}
public static bool IsFromSameWeek(this DateTime first, DateTime second, DayOfWeek firstDayOfWeek = DayOfWeek.Monday)
{
// sort dates
if (first > second)
{
Swap(ref first, ref second);
}
var daysDiff = (second - first).TotalDays;
if (daysDiff >= 7)
{
return false;
}
const int TotalDaysInWeek = 7;
var adjustedDayOfWeekFirst = (int)first.DayOfWeek + (first.DayOfWeek < firstDayOfWeek ? TotalDaysInWeek : 0);
var adjustedDayOfWeekSecond = (int)second.DayOfWeek + (second.DayOfWeek < firstDayOfWeek ? TotalDaysInWeek : 0);
return adjustedDayOfWeekSecond >= adjustedDayOfWeekFirst;
}
}
Also here is link to another correct solution with slightly different approach.

Find start and end dates for the first date's week. Then check if the second date is between those two.
public static bool DateInsideOneWeek(DateTime date1, DateTime date2)
{
DayOfWeek firstDayOfWeek = System.Globalization.CultureInfo.CurrentCulture.DateTimeFormat.FirstDayOfWeek;
DateTime startDateOfWeek = date1.Date;
while(startDateOfWeek.DayOfWeek != firstWeekDay)
{ startDateOfWeek = startDateOfWeek.AddDays(-1d); }
DateTime endDateOfWeek = startDateOfWeek.AddDays(6d);
return date2 >= startDateOfWeek && date2 <= endDateOfWeek;
}

If you don't want to use the Calendar class you can use this function:
public static int WeekOfYear(DateTime dt)
{
int startDays = 0;
// first day of the year
DateTime firstJanuary = new DateTime(dt.Year, 1, 1);
if (firstJanuary.DayOfWeek == DayOfWeek.Tuesday)
{
startDays = 1;
}
else if (firstJanuary.DayOfWeek == DayOfWeek.Wednesday)
{
startDays = 2;
}
else if (firstJanuary.DayOfWeek == DayOfWeek.Thursday)
{
startDays = 3;
}
else if (firstJanuary.DayOfWeek == DayOfWeek.Friday)
{
startDays = 4;
}
else if (firstJanuary.DayOfWeek == DayOfWeek.Saturday)
{
startDays = 5;
}
else if (firstJanuary.DayOfWeek == DayOfWeek.Sunday)
{
startDays = 6;
}
if (DateTimeFormatInfo.CurrentInfo.FirstDayOfWeek == DayOfWeek.Sunday)
{
startDays++;
startDays = startDays % 7;
}
return ((dt.DayOfYear + startDays - 1) / 7) + 1;
}

Accepted answer doesn't work for a french calendar and when the dates are 03/10/2022 and 09/10/2022.
This worked for me :
public static partial class DateTimeExtensions
{
public static DateTime FirstDayOfWeek(this DateTime dt)
{
var culture = System.Threading.Thread.CurrentThread.CurrentCulture;
var diff = dt.DayOfWeek - culture.DateTimeFormat.FirstDayOfWeek;
if (diff < 0)
{
diff += 7;
}
return dt.AddDays(-diff).Date;
}
public static DateTime LastDayOfWeek(this DateTime dt) =>
dt.FirstDayOfWeek().AddDays(6);
public static DateTime FirstDayOfMonth(this DateTime dt) =>
new DateTime(dt.Year, dt.Month, 1);
public static DateTime LastDayOfMonth(this DateTime dt) =>
dt.FirstDayOfMonth().AddMonths(1).AddDays(-1);
public static DateTime FirstDayOfNextMonth(this DateTime dt) =>
dt.FirstDayOfMonth().AddMonths(1);
public static int GetWeeekNumber(this DateTime dt)
{
CultureInfo culture = System.Threading.Thread.CurrentThread.CurrentCulture;
Calendar myCal = culture.Calendar;
// Gets the DTFI properties required by GetWeekOfYear.
CalendarWeekRule myCWR = culture.DateTimeFormat.CalendarWeekRule;
DayOfWeek myFirstDOW = culture.DateTimeFormat.FirstDayOfWeek;
return myCal.GetWeekOfYear(dt, myCWR, myFirstDOW);
}
public static bool IsInTheSameWeek(this DateTime date1, DateTime date2)
{
return date1.GetWeeekNumber() == date2.GetWeeekNumber();
}
}
Usage :
item.Week.IsInTheSameWeek(Week)

Adding Days to a Date but Excluding Weekends

Given a date how can I add a number of days to it, but exclude weekends. For example, given 11/12/2008 (Wednesday) and adding five will result in 11/19/2008 (Wednesday) rather than 11/17/2008 (Monday).
I can think of a simple solution like looping through each day to add and checking to see if it is a weekend, but I'd like to see if there is something more elegant. I'd also be interested in any F# solution.

using Fluent DateTime https://github.com/FluentDateTime/FluentDateTime
var dateTime = DateTime.Now.AddBusinessDays(4);

public DateTime AddBusinessDays(DateTime dt, int nDays)
{
int weeks = nDays / 5;
nDays %= 5;
while(dt.DayOfWeek == DayOfWeek.Saturday || dt.DayOfWeek == DayOfWeek.Sunday)
dt = dt.AddDays(1);
while (nDays-- > 0)
{
dt = dt.AddDays(1);
if (dt.DayOfWeek == DayOfWeek.Saturday)
dt = dt.AddDays(2);
}
return dt.AddDays(weeks*7);
}

Without over-complicating the algorithm, you could just create an extension method like this:
public static DateTime AddWorkingDays(this DateTime date, int daysToAdd)
{
while (daysToAdd > 0)
{
date = date.AddDays(1);
if (date.DayOfWeek != DayOfWeek.Saturday && date.DayOfWeek != DayOfWeek.Sunday)
{
daysToAdd -= 1;
}
}
return date;
}

I would use this extension, remember since it is an extension method to put it in a static class.
Usage:
var dateTime = DateTime.Now.AddBusinessDays(5);
Code:
namespace ExtensionMethods
{
public static class MyExtensionMethods
{
public static DateTime AddBusinessDays(this DateTime current, int days)
{
var sign = Math.Sign(days);
var unsignedDays = Math.Abs(days);
for (var i = 0; i < unsignedDays; i++)
{
do
{
current = current.AddDays(sign);
} while (current.DayOfWeek == DayOfWeek.Saturday ||
current.DayOfWeek == DayOfWeek.Sunday);
}
return current;
}
}
}
Source:
https://github.com/FluentDateTime/FluentDateTime/blob/master/src/FluentDateTime/DateTime/DateTimeExtensions.cs

int daysToAdd = weekDaysToAdd + ((weekDaysToAdd / 5) * 2) + (((origDate.DOW + (weekDaysToAdd % 5)) >= 5) ? 2 : 0);
To wit; the number of "real" days to add is the number of weekdays you're specifying, plus the number of complete weeks that are in that total (hence the weekDaysToAdd / 5) times two (two days in the weekend); plus a potential offset of two days if the original day of the week plus the number of weekdays to add "within" the week (hence the weekDaysToAdd mod 5) is greater than or equal to 5 (i.e. is a weekend day).
Note: this works assuming that 0 = Monday, 2 = Tuesday, ... 6 = Sunday. Also; this does not work on negative weekday intervals.

I created an extension that allows you to add or subtract business days.
Use a negative number of businessDays to subtract. It seems to work in all cases.
namespace Extensions.DateTime
{
public static class BusinessDays
{
public static System.DateTime AddBusinessDays(this System.DateTime source, int businessDays)
{
var dayOfWeek = businessDays < 0
? ((int)source.DayOfWeek - 12) % 7
: ((int)source.DayOfWeek + 6) % 7;
switch (dayOfWeek)
{
case 6:
businessDays--;
break;
case -6:
businessDays++;
break;
}
return source.AddDays(businessDays + ((businessDays + dayOfWeek) / 5) * 2);
}
}
}
Example:
using System;
using System.Windows.Forms;
using Extensions.DateTime;
namespace AddBusinessDaysTest
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
label1.Text = DateTime.Now.AddBusinessDays(5).ToString();
label2.Text = DateTime.Now.AddBusinessDays(-36).ToString();
}
}
}

F# flavor of http://stackoverflow.com/questions/1044688 's answer:
namespace FSharpBasics
module BusinessDays =
open System;
let private weekLength = 5
(*operation*)
let addBusinessDays (numberOfBusinessDays: int) (startDate: DateTime) =
let startWeekDay = startDate.DayOfWeek
let sign = Math.Sign(numberOfBusinessDays)
let weekendSlide, businessDaysSlide =
match startWeekDay with
| DayOfWeek.Saturday when sign > 0 -> (2, -1)
| DayOfWeek.Saturday when sign < 0 -> (-1, 1)
| DayOfWeek.Sunday when sign > 0 -> (1, -1)
| DayOfWeek.Sunday when sign < 0 -> (-2, 1)
| _ -> (0, 0)
let baseStartDate = startDate.AddDays (float weekendSlide)
let days = Math.Abs (numberOfBusinessDays + businessDaysSlide) % weekLength
let weeks = Math.Abs (numberOfBusinessDays + businessDaysSlide) / weekLength
let baseWeekDay = int baseStartDate.DayOfWeek
let oneMoreWeekend =
if sign = 1 && days + baseWeekDay > 5 || sign = -1 && days >= baseWeekDay then 2
else 0
let totalDays = (weeks * 7) + days + oneMoreWeekend
baseStartDate.AddDays (float totalDays)
[<EntryPoint>]
let main argv =
let now = DateTime.Now
printfn "Now is %A" now
printfn "13 business days from now would be %A" (addBusinessDays 13 now)
System.Console.ReadLine() |> ignore
0

This is better if anyone is looking for a TSQL solution. One line of code and works with negatives.
CREATE FUNCTION[dbo].[AddBusinessDays](#Date date,#n INT)RETURNS DATE AS BEGIN
DECLARE #d INT;SET #d=4-SIGN(#n)*(4-DATEPART(DW,#Date));
RETURN DATEADD(D,#n+((ABS(#n)+#d-2)/5)*2*SIGN(#n)-#d/7,#Date)END

Here is how I did it.
I had to calculate SLA (Service Level Agreement) due dates based on a start date and number of days, and account for weekends and public holidays:
public DateTime? CalculateSLADueDate(DateTime slaStartDateUTC, double slaDays)
{
if (slaDays < 0)
{
return null;
}
var dayCount = slaDays;
var dueDate = slaStartDateUTC;
var blPublicHoliday = new PublicHoliday();
IList<BusObj.PublicHoliday> publicHolidays = blPublicHoliday.SelectAll();
do
{
dueDate = dueDate.AddDays(1);
if ((dueDate.DayOfWeek != DayOfWeek.Saturday)
&& (dueDate.DayOfWeek != DayOfWeek.Sunday)
&& !publicHolidays.Any(x => x.HolidayDate == dueDate.Date))
{
dayCount--;
}
}
while (dayCount > 0);
return dueDate;
}
blPublicHoliday.SelectAll() is a cached in-memory list of public holidays.
(note: this is a cut down version for sharing publicly, there is a reason its not an extension method)

enter code public static DateTime AddWorkDays(DateTime dt,int daysToAdd)
{
int temp = daysToAdd;
DateTime endDateOri = dt.AddDays(daysToAdd);
while (temp !=0)
{
if ((dt.AddDays(temp).DayOfWeek == DayOfWeek.Saturday)|| (dt.AddDays(temp).DayOfWeek == DayOfWeek.Sunday))
{
daysToAdd++;
temp--;
}
else
{
temp--;
}
}
while (endDateOri.AddDays(temp) != dt.AddDays(daysToAdd))
{
if ((dt.AddDays(temp).DayOfWeek == DayOfWeek.Saturday) || (dt.AddDays(temp).DayOfWeek == DayOfWeek.Sunday))
{
daysToAdd++;
}
temp++;
}
// final enddate check
if (dt.AddDays(daysToAdd).DayOfWeek == DayOfWeek.Saturday)
{
daysToAdd = daysToAdd + 2;
}
else if (dt.AddDays(daysToAdd).DayOfWeek == DayOfWeek.Sunday)
{
daysToAdd++;
}
return dt.AddDays(daysToAdd);
}

DateTime oDate2 = DateTime.Now;
int days = 8;
for(int i = 1; i <= days; i++)
{
if (oDate.DayOfWeek == DayOfWeek.Saturday)
{
oDate = oDate.AddDays(2);
}
if (oDate.DayOfWeek == DayOfWeek.Sunday)
{
oDate = oDate.AddDays(1);
}
oDate = oDate.AddDays(1);
}

Given the number of the original day in the year D and original day in the week W and the number of workdays to add N, the next weekday number is
W + N % 5.
The next day in the year (with no wraparound check) is
D + ((N / 5) * 7) + N % 5).
This is assuming that you have integer division.

Formula will be: Workday(date,no.of days,(weekday(1)))
Try this. This will help.