如何在 lambda function c# 的位置中使用列表？

Question

I have this code now and I would like to use a list of weekend instead of static days Sunday and Saturday . How can I use the equal function between an item z.DayOfWeek and a list of weekend.

    DateTime start = new DateTime(2021,3,3);
    DateTime end = new DateTime(2021,3,27);
    
    List<DateTime> blackOut = new List<DateTime>
    {
        new DateTime(2021,3,10),
        new DateTime(2021,3,11)
        
    };
    
var days = Enumerable.Range(0, (int)(end - start).TotalDays)
          .Select(x => start.AddDays(x))
          .Where(z => z.DayOfWeek != DayOfWeek.Saturday && 
                      z.DayOfWeek != DayOfWeek.Sunday &&
                      !blackOut.Contains(z))
          .Count();

Suppose that I have a list that contains weekend called weekendslist, what I have tried is:

List<string> weekendslist = new List<string>();
weekendslist.Add(DayOfWeek.Saturday.ToString());
weekendslist.Add(DayOfWeek.Sunday.ToString());
var days = Enumerable.Range(0, (int)(end - start).TotalDays)
          .Select(x => start.AddDays(x))
          .Where(z => weekendslist.Contains(z.DayOfWeek.ToString())
                      !blackOut.Contains(z))
          .Count();

But this does not work for me. Anyone have any idea how can I do to achieve this?

Ref: How to exclude blackout days from a specific duration between two dates chosen from a two Datepicker? C#

Answer 1

How about using Enum.IsDefined ?

enum Weekends
{
    Saturday,
    Sunday
}

var days = Enumerable.Range(0, (int)(end - start).TotalDays)
    .Select(x => start.AddDays(x))
    .Where(z => Enum.IsDefined(typeof(Weekends), z.DayOfWeek.ToString()) &&
                !blackOut.Contains(z))
    .Count();

Or another option would be to write an extension for DayOfWeek

public static class WeekendExtension
{
    public static bool IsWeekend(this DayOfWeek dayOfWeek)
    {
        return dayOfWeek == DayOfWeek.Saturday || 
            dayOfWeek == DayOfWeek.Sunday;
    }
}

var days = Enumerable.Range(0, (int)(end - start).TotalDays)
    .Select(x => start.AddDays(x))
    .Where(z => !z.DayOfWeek.IsWeekend() &&
                !blackOut.Contains(z))
    .Count();

Answer 2

The following code is the same as your attempt, only using DayOfWeek enum values instead of strings, and properly negating the Contains :

DateTime start = new DateTime(2021, 3, 3);
DateTime end = new DateTime(2021, 3, 27);
List<DateTime> blackOut = new List<DateTime>
{
    new DateTime(2021, 3, 10), 
    new DateTime(2021, 3, 11)
};
List<DayOfWeek> weekendslist = new List<DayOfWeek>
{
    DayOfWeek.Saturday,
    DayOfWeek.Sunday
};
var days = Enumerable
    .Range(0, (int)(end - start).TotalDays)
    .Select(x => start.AddDays(x))
    .Where(z => 
           !weekendslist.Contains(z.DayOfWeek) && 
           !blackOut.Contains(z))
    .Count();
Console.WriteLine(days);