using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var closedOn = new DayOfWeek[] { DayOfWeek.Saturday, DayOfWeek.Sunday };

        var start = new DateTime(2018, 07, 23);

        var end = new DateTime(2018, 08, 06);

        var days1 = GetBusinessDaysInRange(start, end, closedOn);

        foreach(var day in days1) {

            Console.WriteLine(day.ToLongDateString());

        }

        Console.WriteLine("___________________");

        var days2 = GetFixedNumberOfBusinessDays(start, 10, closedOn);

        foreach(var day in days2) {

            Console.WriteLine(day.ToLongDateString());

        }

    }

    // Returns a list of the dates of the Business Days between the given start and end date

    public static IEnumerable<DateTime> GetBusinessDaysInRange(DateTime startDate, DateTime endDate, DayOfWeek[] closedOn) {

        if (endDate < startDate) {

            throw new ArgumentException("endDate must be before startDate");    

        }

        var businessDays = new List<DateTime>();

        var date = startDate;

        while (date < endDate) {

            if (!closedOn.Contains(date.DayOfWeek)) {

                businessDays.Add(date);

            }

            date = date.AddDays(1);

        }

        return businessDays;

    }

    // Returns a list of the dates of the Business Days from the given start with the given number of days

    public static IEnumerable<DateTime> GetFixedNumberOfBusinessDays(DateTime startDate, int numberOfBusinessDays, DayOfWeek[] closedOn) {

        if (numberOfBusinessDays < 0) {

             throw new ArgumentException("numberOfBusinessDays must be zero or positive."); 

        }

        var businessDays = new List<DateTime>();

        var date = startDate;

        while (businessDays.Count() < numberOfBusinessDays) {

            if (!closedOn.Contains(date.DayOfWeek)) {

                businessDays.Add(date);

            }

            date = date.AddDays(1);

        }

        return businessDays;

    }

}