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.

maximum and minimum value in list

I'm currently doing my current project and I had a problem. Here's what the project needs to do:
Find the maximum and the minimum temperature from a certain range of date. The range of the date will be inputted by the user.
So, I make a form as the main menu for inputting the items and finding the maximum and minimum value (both in the new form). I also make a class to store the items:
public class TempDate
{
public double Temp { get; set; }
public DateTime Date { get; set; }
}
In the first form, just call it FormAddData, from here items will be stored into the list using a textbox and here's the code:
private void buttonSubmit_Click(object sender, EventArgs e)
{
FormMenu formMenu = (FormMenu)this.Owner;
DateTime date = dateTimePickerDate.Value.Date;
double temp = double.Parse(textBoxTemp.Text);
TempDate tempDate = new TempDate();
tempDate.Date = date;
tempDate.Temp = temp;
formMenu.listOfTempDate.Add(tempDate);
listBoxInfo.Items.Add(date + "\t" + temp + "°C");
}
In the second form that called FormMaxMinRange. In this form, I use two DateTimePicker the first one for the starting date and the second for the ending date. From here I need to make a button that will select all the items from the range that I used from starting and ending date. Here's my code:
private void buttonMaxMin_Click(object sender, EventArgs e)
{
FormMenu formMenu = (FormMenu)this.Owner;
DateTime start = dateTimePickerStart.Value.Date;
DateTime end = dateTimePickerEnd.Value.Date;
int highest = 0;
double max = formMenu.listOfTempDate[0].Temp;
int lowest = 0;
double min = formMenu.listOfTempDate[0].Temp;
for (int i = 1; i < formMenu.listOfTempDate.Count; i++)
{
if (formMenu.listOfTempDate[i].Date >= start
&& formMenu.listOfTempDate[i].Date <= end)
{
if (formMenu.listOfTempDate[i].Temp > max)
{
highest = i;
max = formMenu.listOfTempDate[i].Temp;
}
if (formMenu.listOfTempDate[i].Temp < min)
{
lowest = i;
min = formMenu.listOfTempDate[i].Temp;
}
}
}
listBoxMaxMin.Items.Add("");
listBoxMaxMin.Items.Add("Lowest temp: " + min + ", on " + formMenu.listOfTempDate[lowest].Date);
listBoxMaxMin.Items.Add("Highest temp: " + max + ", on " + formMenu.listOfTempDate[highest].Date);
}
Here's the main form that i declared the class (which include the list):
public partial class FormMenu : Form
{
public List<TempDate> listOfTempDate = new List<TempDate>();
public FormMenu()
{
InitializeComponent();
}
private void fromCertainRangeToolStripMenuItem_Click(object sender, EventArgs e)
{
FormMaxMinRange formMaxMinRange = new FormMaxMinRange();
formMaxMinRange.Owner = this;
formMaxMinRange.ShowDialog();
}
}
But, the problem is, the minimum value was not selected inside the range of selection. Also I want the max and min value was printed in the listbox. Sorry for the long and weird question. I hope someone can understand what I means with this question to complete my project. Thank you.

See this code snippet.
You can use Linq to select the reduced list (with Start/Enddate) and order it by Temp. Now you can easy select the first (min) and the last (max) object.
List<TempDate> loTempDateList = new List<TempDate>()
{
new TempDate() {Date = DateTime.Now.AddDays(-10), Temp = 10.01 },
new TempDate() {Date = DateTime.Now.AddDays(-5), Temp = 20.01 },
new TempDate() {Date = DateTime.Now.AddDays(-3), Temp = 30.01 },
new TempDate() {Date = DateTime.Now, Temp = 40.01 }
};
DateTime ldStart = DateTime.Now.AddDays(-6);
DateTime ldEnd = DateTime.Now.AddDays(-1);
var loDateList = loTempDateList.Where(item => item.Date <= ldEnd && item.Date >= ldStart)
.OrderBy(item => item.Temp);
TempDate loMin = loDateList.First();
TempDate loMax = loDateList.Last();
Console.WriteLine("{0}: {1} with max temp", loMax.Date, loMax.Temp);
Console.WriteLine("{0}: {1} with min temp", loMin.Date, loMin.Temp);
Output (for today):
9/26/2017 3:17:09 PM: 30.01 with max temp
9/24/2017 3:17:09 PM: 20.01 with min temp
Update (with your variable names):
Copy this under DateTime end = dateTimePickerEnd.Value.Date;in your Form
var loDateList = listOfTempDate.Where(item => item.Date <= end && item.Date >= start)
.OrderBy(item => item.Temp);
TempDate loMin = loDateList.FirstOrDefault();
TempDate loMax = loDateList.LastOrDefault();
if (loMin != null && loMax != null)
{
listBoxMaxMin.Items.Add("");
listBoxMaxMin.Items.Add("Lowest temp: " + loMin.Temp + ", on " + loMin.Date);
listBoxMaxMin.Items.Add("Highest temp: " + loMax.Temp + ", on " + loMax.Date);
}

I would suggest you use Linq Max and Min methods.
// filter out only the dates in the range you need
var items = formMenu.listOfTempDateWhere(
item => ((TempDate)item).Date >= start && ((TempDate)item).Date <= end
);
// get the maximum value
var max = items.Max(item => item.Temp);
// get the minimum value
var min = items.Min(item => item.Temp);
Just remember to add using System.Linq on the top of your .cs file
try this online

If you don't like a LINQ approach (I never use LINQ, for some, possibly invalid reason, I think it's evil), you can override the List class and extend it with methods of your own.
public class TempDataList<T> : List<TempData>
{
public TempDataList() : base()
{
}
public TempDataList(IEnumerable<TempData> collection) : base(collection)
{
}
public TempData GetMaxTemp(DateTime startDate, DateTime endDate)
{
TempData highestTempData = null;
for (int i = 0; i < this.Count; i++)
{
if (this[i].Date >= startDate && this[i].Date <= endDate)
{
if (highestTempData == null || this[i].Temp > highestTempData.Temp)
{
highestTempData = this[i];
}
}
}
return highestTempData;
}
public TempData GetMinTemp(DateTime startDate, DateTime endDate)
{
TempData lowestTempData = null;
for (int i = 0; i < this.Count; i++)
{
if (this[i].Date >= startDate && this[i].Date <= endDate)
{
if (lowestTempData == null || this[i].Temp < lowestTempData.Temp)
{
lowestTempData = this[i];
}
}
}
return lowestTempData;
}
}
And fill the extended list and call the methods:
TempDataList<TempData> tempDataList = new TempDataList<TempData>();
tempDataList.Add(new TempData(10, DateTime.UtcNow));
tempDataList.Add(new TempData(20, DateTime.UtcNow));
tempDataList.Add(new TempData(15, DateTime.MinValue));
tempDataList.Add(new TempData(25, DateTime.MaxValue));
Console.WriteLine(tempDataList.GetMaxTemp(DateTime.UtcNow.AddDays(-1), DateTime.UtcNow.AddDays(1)).Temp);
Console.WriteLine(tempDataList.GetMinTemp(DateTime.UtcNow.AddDays(-1), DateTime.UtcNow.AddDays(1)).Temp);

Multiple computation of datetime from database to C#

can someone help me with my payroll system codes. I want a result where i will get the total number of hours of each employee and before proceeding to another employee it will be saved in a table in mysql. the problems im encountering are
1. it still counts the datetime even if it is null in database.
2. after changing the timeline it still counts the previous total hours
the variable does not reset.
enter image description here
public int IdFrom;
public int Idto;
public int TotalHours;
public int day;
public DateTime time1;
public DateTime time2;
public string testNull;
public string date;
public string testvariable;
string testdate1;
string testdate2;
TimeSpan totaltime;
TimeSpan ts;
private void btn_compute_Click(object sender, EventArgs e)
{
if (rb_all.Checked == true)
{
cls.Connection();
cls.connect.Open();
cls.command = new MySqlCommand("select ID from tbl_attendance order by ID asc limit 1", cls.connect);
cls.reader = cls.command.ExecuteReader();
while (cls.reader.Read())
{
IdFrom = cls.reader.GetInt16(0);
}
cls.reader.Close();
cls.Connection();
cls.connect.Open();
cls.command = new MySqlCommand("select ID from tbl_attendance order by ID desc limit 1", cls.connect);
cls.reader = cls.command.ExecuteReader();
while (cls.reader.Read())
{
Idto = cls.reader.GetInt16(0);
}
cls.reader.Close();
for(int x = IdFrom;x<=Idto;x++)
{
totaltime = TimeSpan.Zero;
ts = TimeSpan.Zero;
day = 0;
TotalHours = 0;
testNull = "";
date = "";
DateTime dt = DateTime.Parse(start_date.Text);
DateTime dt2 = DateTime.Parse(end_date.Text);
ts = dt2 - dt;
day = ts.Days;
for (int y = 0; y <= day; y++)
{
date = dt.AddDays(y).ToString("yyyy")
+ "-" + dt.AddDays(y).ToString("MM")
+ "-" + dt.AddDays(y).ToString("dd");
cls.Connection();
cls.connect.Open();
cls.command = new MySqlCommand("select Time_In,Time_Out from tbl_attendance where Date = '" + date + "' and ID = "+x+"", cls.connect);
cls.reader = cls.command.ExecuteReader();
while (cls.reader.Read())
{
time1 = DateTime.Parse(cls.reader.GetValue(0).ToString());
time2 = DateTime.Parse(cls.reader.GetValue(1).ToString());
}
cls.reader.Close();
MessageBox.Show(time1.ToString());
MessageBox.Show(time2.ToString());
totaltime = time2 - time1;
MessageBox.Show(totaltime.Hours.ToString());
if (totaltime.Hours == 0)
{
}
else
{
TotalHours = TotalHours + (int.Parse(totaltime.Hours.ToString()) - 1);
}
}//total hours computed
if (totaltime.Hours == 0)
{
break;
}
else
{
MessageBox.Show(TotalHours.ToString());
break;
}
}//end of for loop for total number of hours
}

Regex c# - where to insert the blank space

I want to allow the user to enter the year in blank but I don´t know where to put \s\s\s\s in the following expression.
Here is an example of what I need to do: if the user inserts 03-07-_____ the program must be executed every 3Th of July of each year(and it proceeds the same way if the user inserts blank date, month or year or twoo of this three)
System.Text.RegularExpressions.Regex rdate =
new System.Text.RegularExpressions.Regex(#"^((((0?[1-9]|[12]\d|3[01]|\s\s|\s\d)[\-](0?[13578]|1[02]|\s\s)[\-]((1[6-9]|[2-9]\d)?\d{2}))|((0?[1-9]|[12]\d|30)[\-](0?[13456789]|1[012])[\-]((1[6-9]|[2-9]\d)?\d{2}))|((0?[1-9]|1\d|2[0-8])[\-]0?2[\-]((1[6-9]|[2-9]\d)?\d{2}))|(29[\-]0?2[\-]((1[6-9]|[2-9]\d)?(0[48]|[2468][048]|[13579][26])|((16|[2468][048]|[3579][26])00)|00)))|(((0[1-9]|[12]\d|3[01])(0[13578]|1[02])((1[6-9]|[2-9]\d)?\d{2}))|((0[1-9]|[12]\d|30)(0[13456789]|1[012])((1[6-9]|[2-9]\d)?\d{2}))|((0[1-9]|1\d|2[0-8])02((1[6-9]|[2-9]\d)?\d{2}))|(2902((1[6-9]|[2-9]\d)?(0[48]|[2468][048]|[13579][26])|((16|[2468][048]|[3579][26])00)|00))))$");
Could someone help me?(this expression validates even a leap year)

Here is what You asked for
System.Text.RegularExpressions.Regex rdate =
new System.Text.RegularExpressions.Regex(#"^((((0?[1-9]|[12]\d|3[01]|\s\s|\s\d)[\-](0?[13578]|1[02]|\s\s)[\-]((1[6-9]|[2-9]\d)?\d{2}|\s\s\s\s))|((0?[1-9]|[12]\d|30)[\-](0?[13456789]|1[012])[\-]((1[6-9]|[2-9]\d)?\d{2}|\s\s\s\s))|((0?[1-9]|1\d|2[0-8])[\-]0?2[\-]((1[6-9]|[2-9]\d)?\d{2}|\s\s\s\s))|(29[\-]0?2[\-]((1[6-9]|[2-9]\d)?(0[48]|[2468][048]|[13579][26])|((16|[2468][048]|[3579][26])00)|00|\s\s\s\s)))|(((0[1-9]|[12]\d|3[01])(0[13578]|1[02])((1[6-9]|[2-9]\d)?\d{2}))|((0[1-9]|[12]\d|30)(0[13456789]|1[012])((1[6-9]|[2-9]\d)?\d{2}))|((0[1-9]|1\d|2[0-8])02((1[6-9]|[2-9]\d)?\d{2}))|(2902((1[6-9]|[2-9]\d)?(0[48]|[2468][048]|[13579][26])|((16|[2468][048]|[3579][26])00)|00))))$");
But I am not sure it is what You really want. The regex was already patched, I continued the way. But not only it is maintenance nightmare, it behaves strange. It accepts empty day, but only when month is january, march, may... or empty. Less lines of code is not always better. I would suggest to rewrite it completely. Something simmilar to this:
protected DateTime? getDateTimeFromParts(string day, string month, string year)
{
DateTime now = DateTime.Now;
int iyear;
if (string.IsNullOrWhiteSpace(year))
{
iyear = now.Year;
}
else
{
iyear = int.Parse(year);
if (iyear >= 0 && iyear < 100) { iyear += 2000; }
}
int imonth;
if (string.IsNullOrWhiteSpace(month))
{
imonth = now.Month;
}
else
{
imonth = int.Parse(month);
}
int iday;
if (string.IsNullOrWhiteSpace(day))
{
iday = now.Day;
}
else
{
iday = int.Parse(day);
}
if (iyear <= DateTime.MaxValue.Year && iyear >= DateTime.MinValue.Year)
{
if (imonth >= 1 && imonth <= 12)
{
if (DateTime.DaysInMonth(iyear, imonth) >= iday && iday >= 1)
return new DateTime(iyear, imonth, iday);
}
}
return null;
}
protected DateTime? getDateTime(string dateStr)
{
Regex r = new Regex(#"^(\d\d)(\d\d)((\d\d)?\d\d)$");
Match m = r.Match(dateStr);
if (m.Success)
{
return getDateTimeFromParts(m.Groups[1].Value, m.Groups[2].Value, m.Groups[3].Value);
}
r = new Regex(#"^(\d?\d|\s\d|\s\s)[-](\d?\d|\s\s)[-]((\d\d)?\d\d|\s\s\s\s)$");
m = r.Match(dateStr);
if (m.Success)
{
return getDateTimeFromParts(m.Groups[1].Value, m.Groups[2].Value, m.Groups[3].Value);
}
return null;
}

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.