AddBusinessDays and GetBusinessDays
For me I had to have a solution that would skip weekends and go in either negative or positive. My criteria was if it went forward and landed on a weekend it would need to advance to Monday. If it was going back and landed on a weekend it would have to jump to Friday.
For example:
- Wednesday - 3 business days = Last Friday
- Wednesday + 3 business days = Monday
- Friday - 7 business days = Last Wednesday
- Tuesday - 5 business days = Last Tuesday
Well you get the idea ;)
I ended up writing this extension class
public static partial class MyExtensions
{
public static DateTime AddBusinessDays(this DateTime date, int addDays)
{
while (addDays != 0)
{
date = date.AddDays(Math.Sign(addDays));
if (MyClass.IsBusinessDay(date))
{
addDays = addDays - Math.Sign(addDays);
}
}
return date;
}
}
It uses this method I thought would be useful to use elsewhere...
public class MyClass
{
public static bool IsBusinessDay(DateTime date)
{
switch (date.DayOfWeek)
{
case DayOfWeek.Monday:
case DayOfWeek.Tuesday:
case DayOfWeek.Wednesday:
case DayOfWeek.Thursday:
case DayOfWeek.Friday:
return true;
default:
return false;
}
}
}
If you don't want to bother with that you can just replace out if (MyClass.IsBusinessDay(date))
with if if ((date.DayOfWeek != DayOfWeek.Saturday) && (date.DayOfWeek != DayOfWeek.Sunday))
So now you can do
var myDate = DateTime.Now.AddBusinessDays(-3);
or
var myDate = DateTime.Now.AddBusinessDays(5);
Here are the results from some testing:
Test Expected Result Wednesday -4 business days Thursday Thursday Wednesday -3 business days Friday Friday Wednesday +3 business days Monday Monday Friday -7 business days Wednesday Wednesday Tuesday -5 business days Tuesday Tuesday Friday +1 business days Monday Monday Saturday +1 business days Monday Monday Sunday -1 business days Friday Friday Monday -1 business days Friday Friday Monday +1 business days Tuesday Tuesday Monday +0 business days Monday Monday
I created an extension that allows you to add or subtract business days. Use a negative number of businessDays to subtract. I think it's quite an elegant solution. 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();
}
}
}
Latest attempt for your first function:
public static DateTime AddBusinessDays(DateTime date, int days)
{
if (days < 0)
{
throw new ArgumentException("days cannot be negative", "days");
}
if (days == 0) return date;
if (date.DayOfWeek == DayOfWeek.Saturday)
{
date = date.AddDays(2);
days -= 1;
}
else if (date.DayOfWeek == DayOfWeek.Sunday)
{
date = date.AddDays(1);
days -= 1;
}
date = date.AddDays(days / 5 * 7);
int extraDays = days % 5;
if ((int)date.DayOfWeek + extraDays > 5)
{
extraDays += 2;
}
return date.AddDays(extraDays);
}
The second function, GetBusinessDays, can be implemented as follows:
public static int GetBusinessDays(DateTime start, DateTime end)
{
if (start.DayOfWeek == DayOfWeek.Saturday)
{
start = start.AddDays(2);
}
else if (start.DayOfWeek == DayOfWeek.Sunday)
{
start = start.AddDays(1);
}
if (end.DayOfWeek == DayOfWeek.Saturday)
{
end = end.AddDays(-1);
}
else if (end.DayOfWeek == DayOfWeek.Sunday)
{
end = end.AddDays(-2);
}
int diff = (int)end.Subtract(start).TotalDays;
int result = diff / 7 * 5 + diff % 7;
if (end.DayOfWeek < start.DayOfWeek)
{
return result - 2;
}
else{
return result;
}
}
using Fluent DateTime:
var now = DateTime.Now;
var dateTime1 = now.AddBusinessDays(3);
var dateTime2 = now.SubtractBusinessDays(5);
internal code is as follows
/// <summary>
/// Adds the given number of business days to the <see cref="DateTime"/>.
/// </summary>
/// <param name="current">The date to be changed.</param>
/// <param name="days">Number of business days to be added.</param>
/// <returns>A <see cref="DateTime"/> increased by a given number of business days.</returns>
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;
}
/// <summary>
/// Subtracts the given number of business days to the <see cref="DateTime"/>.
/// </summary>
/// <param name="current">The date to be changed.</param>
/// <param name="days">Number of business days to be subtracted.</param>
/// <returns>A <see cref="DateTime"/> increased by a given number of business days.</returns>
public static DateTime SubtractBusinessDays(this DateTime current, int days)
{
return AddBusinessDays(current, -days);
}