canvasManagement/Management.Web/Shared/Semester/MonthDetail.razor

@using System.Linq;
@code
{
  [Parameter, EditorRequired]
  public CalendarMonth Month { get; set; } = default!;

  [Parameter, EditorRequired]
  public SemesterPlanner Semester { get; set; } = default!;
  public DayOfWeek[] WeekDaysList { get => (DayOfWeek[])Enum.GetValues(typeof(DayOfWeek)); }

  public string MonthName { get => Month?.DaysByWeek.First().FirstOrDefault(d => d != null)?.ToString("MMMM") ?? ""; }
}

<h3 class="text-center">
  @MonthName
</h3>

<div class="row text-center fw-bold">
  @foreach (DayOfWeek day in WeekDaysList)
  {
    <div class="@(Semester.Days.Contains(day) ? "col" : "col text-secondary")">@day</div>
  }
</div>

@foreach (var week in Month.DaysByWeek)
{
  <div class="row m-3">
  @foreach (var day in week)
    {

      var baseClasses = "col border rounded rounded-3 pb-5 m-1";
      DayOfWeek? weekDay = day?.DayOfWeek;
      if (weekDay != null)
      {
        DayOfWeek notNullDay = weekDay ?? default;
        var dayInSemester = Semester.Days.Contains(notNullDay) && day < Semester.LastDay && day > Semester.FirstDay;
        var totalClasses = dayInSemester ? $"bg-light {baseClasses}" : baseClasses;
        <div class="@totalClasses">@day?.Day</div>
      }
      else
      {
        <div class="@baseClasses"></div>
      }
    }
  </div>
}