如何在 lambda 函数 c# 的 Where 中使用列表？

Question

我现在有这段代码，我想使用周末列表而不是静态日期 Sunday 和 Saturday 。如何在项目z.DayOfWeek和周末列表之间使用相等函数。

    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();

假设我有一个包含周末的列表周末列表，我尝试过的是：

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();

但这对我不起作用。任何人都知道我该怎么做才能做到这一点？

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

Answer 1

以下代码与您的尝试相同，仅使用DayOfWeek 枚举值而不是字符串，并正确否定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);

Answer 2

用Enum.IsDefined怎么样？

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();

或者另一种选择是为DayOfWeek写一个扩展

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();