AddBusinessDays and GetBusinessDays

Question

I need to find 2 elegant complete implementations of ``` public static DateTime AddBusinessDays(this DateTime date, int days) { // code here } and public static int GetBusinessDays(this DateTime start, DateTime end) { // code here } ``` O(1) preferable (no loops). EDIT: By business days i mean working days (Monday, Tuesday, Wednesday, Thursday, Friday). No holidays, just weekends excluded. I already have some ugly solutions that seem to work but i wonder if there are elegant ways to do this. Thanks This is what i've written so far. It works in all cases and does negatives too. Still need a GetBusinessDays implementation ``` public static DateTime AddBusinessDays(this DateTime startDate, int businessDays) { int direction = Math.Sign(businessDays); if(direction == 1) { if(startDate.DayOfWeek == DayOfWeek.Saturday) { startDate = startDate.AddDays(2); businessDays = businessDays - 1; } else if(startDate.DayOfWeek == DayOfWeek.Sunday) { startDate = startDate.AddDays(1); businessDays = busi…

Accepted Answer

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;
    }
}
```

AddBusinessDays and GetBusinessDays

Solution

Problem

Related problems