Day of the Week library

Some applications may need a Day Of The Week object. The application may be a business tool that may need to track something based on the day of the week, such as business hours. The application I am designing is using a bus schedule, which varies depending on if it's a weekday or on a weekend. A useful feature of such a class is: given today, what is tomorrow? It works the other way as well. If today is Tuesday, was yesterday a weekday? Is four days from today on a weekend?

DaysOfTheWeekContract.cs


namespace Library.Contracts {
   public enum DaysOfTheWeek {
      Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday
   }
   public enum DayClassification { WeekDay, WeekEnd }
   public interface IDay {
      DaysOfTheWeek DayOfTheWeek { get; }
      DayClassification Classification { get; }
      IDay Next { get; set;  }
      IDay Previous { get; set;  }
   }
   public interface IWeek {
      DayClassification Classification(DaysOfTheWeek day);
      DaysOfTheWeek Tomorrow(DaysOfTheWeek today);
      DaysOfTheWeek Yesterday(DaysOfTheWeek today);
   }
}



DaysOfTheWeekImp.cs

using Library.Contracts;
namespace Library.Impl {
   public sealed class Day : IDay {
      public DaysOfTheWeek DayOfTheWeek { get; private set; }
      public DayClassification Classification { get; private set; }
      public Day(DaysOfTheWeek dayOfTheWeek, DayClassification classification) {
         this.DayOfTheWeek = dayOfTheWeek;
         this.Classification = classification;
      }
      public IDay Next { get; set; }
      public IDay Previous { get; set; }
   }


   public sealed class Week : IWeek {
      private IList<IDay> Days;
      public Week() {
         this.Days = new List<IDay>();
         IDay sunday = new Day(DaysOfTheWeek.Sunday, DayClassification.WeekEnd);
         IDay monday = new Day(DaysOfTheWeek.Monday, DayClassification.WeekDay);
         IDay tuesday = new Day(DaysOfTheWeek.Tuesday, DayClassification.WeekDay);
         IDay wednesday = new Day(DaysOfTheWeek.Wednesday, DayClassification.WeekDay);
         IDay thursday = new Day(DaysOfTheWeek.Thursday, DayClassification.WeekDay);
         IDay friday = new Day(DaysOfTheWeek.Friday, DayClassification.WeekDay);
         IDay saturday = new Day(DaysOfTheWeek.Saturday, DayClassification.WeekEnd);
         sunday.Previous = saturday;
         sunday.Next = monday;
         monday.Previous = sunday;
         monday.Next = tuesday;
         tuesday.Previous = monday;
         tuesday.Next = wednesday;
         wednesday.Previous = tuesday;
         wednesday.Next = thursday;
         thursday.Previous = wednesday;
         thursday.Next = friday;
         friday.Previous = thursday;
         friday.Next = saturday;
         saturday.Next = sunday;
         saturday.Previous = friday;

         this.Days.Add(sunday);
         this.Days.Add(monday);
         this.Days.Add(tuesday);
         this.Days.Add(wednesday);
         this.Days.Add(thursday);
         this.Days.Add(friday);
         this.Days.Add(saturday);
      }
      public DayClassification Classification(DaysOfTheWeek today) {
         return this.Days[(int)(today)].Classification;
      }
      private int indexOfToday(DaysOfTheWeek today) {
         return (int)(today);
      }
      public DaysOfTheWeek Tomorrow(DaysOfTheWeek today) {
         return this.Days[(int)(today)].Next.DayOfTheWeek;
      }
      public DaysOfTheWeek Yesterday(DaysOfTheWeek today) {
         return this.Days[(int)(today)].Previous.DayOfTheWeek;
      }
   }
}

Your code would look like this:

:
:
    IWeek week = new Week();
    DaysOfTheWeek today = DaysOfTheWeek.Wednesday;  // munge this from DateTime
    int count = 0;
    while (week.Classification(today) != DayClassification.WeekEnd) {
       today = week.Tomorrow(today);
       count++;
    }
    // count contains the number of days until the weekend.