C# 如何计算不包括特定日期（节假日）的工作日

Question

I read some questions/answers related to functions in C# to calculate the working days (Days from Mondays to Fridays); some uses an extended code to achieve that.

I have a data table with more than 50,000 rows and I required an effective method to calculate this information.

Answer 1

Based on @MiBols answer a more efficient solution will be to use a HashSet<DateTime> instead of a List<DateTime> where search is then in O(1) :

/// <summary> Get working days between two dates (Excluding a list of dates - Holidays) </summary>
/// <param name="dtmCurrent">Current date time</param>
/// <param name="dtmFinishDate">Finish date time</param>
/// <param name="excludedDates">Collection of dates to exclude (Holidays)</param>
public static int fwGetWorkingDays(this DateTime dtmCurrent, DateTime dtmFinishDate, 
                                   HashSet<DateTime> excludedDates)
{
    Func<DateTime, bool> workDay = currentDate => (
        currentDate.DayOfWeek == DayOfWeek.Saturday ||
        currentDate.DayOfWeek == DayOfWeek.Sunday ||
        excludedDates.Contains(currentDate.Date));

    return Enumerable.Range(0, 1 + (dtmFinishDate - dtmCurrent).Days)
        .Count(intDay => workDay(dtmCurrent.AddDays(intDay)));
}

Answer 2

/// <summary> Get working days between two dates (Excluding a list of dates - Holidays) </summary>
/// <param name="dtmCurrent">Current date time</param>
/// <param name="dtmFinishDate">Finish date time</param>
/// <param name="lstExcludedDates">List of dates to exclude (Holidays)</param>
public static int fwGetWorkingDays(this DateTime dtmCurrent, DateTime dtmFinishDate, List<DateTime> lstExcludedDates)
{
    Func<DateTime, bool> workDay = currentDate =>
            (
                currentDate.DayOfWeek == DayOfWeek.Saturday ||
                currentDate.DayOfWeek == DayOfWeek.Sunday ||
                lstExcludedDates.Exists(evalDate => evalDate.Date.Equals(currentDate.Date))
            );

    return Enumerable.Range(0, 1 + (dtmFinishDate - dtmCurrent).Days).Count(intDay => workDay(dtmCurrent.AddDays(intDay)));
}

I created this extension that basically takes two dates and a list of dates to exclude (Holidays). Surprisingly this method is very fast and has a validation to exclude the time from the DateTime when compare against the list of exclusions.

Answer 3

public static int ToBusinessWorkingDays(this DateTime start, DateTime due, DateTime[] holidays)
        {
            return Enumerable.Range(0, (due - start).Days)
                            .Select(a => start.AddDays(a))
                            .Where(a => a.DayOfWeek != DayOfWeek.Sunday)
                            .Where(a => a.DayOfWeek != DayOfWeek.Saturday)
                            .Count(a => !holidays.Any(x => x == a));

        }

Answer 4

I did a mix of two soutions above, inverting the expression to verify workDay and checking if the difference is negative.

public static int GetWorkingDaysUntil(this DateTime dtmCurrent, DateTime dtmFinishDate, HashSet<DateTime> excludedDates)
{
    Func<DateTime, bool> workDay = currentDate => !(currentDate.DayOfWeek == DayOfWeek.Saturday ||
                                                    currentDate.DayOfWeek == DayOfWeek.Sunday ||
                                                    excludedDates.Contains(currentDate.Date));

    var daysDifference = (dtmFinishDate - dtmCurrent).Days;

    return daysDifference > 0 ?
                Enumerable.Range(0, 1 + daysDifference).Count(intDay => workDay(dtmCurrent.AddDays(intDay))) :
                0;
}

Answer 5

While using Gilad Green answer, I found how to get the list of holiday dates so you wouldn't need to make them yourself.

Following live2 answer on Business/Holiday date handling , you may get a list of holiday dates.

Nuget

PM> install-package Nager.Date

Example:

Get all publicHolidays of a year

var publicHolidays = DateSystem.GetPublicHoliday(2018, CountryCode.DE);

You may check if needed country exists in this registry here: https://date.nager.at/Country