example.cs

switch (DateTime.Now.DayOfWeek)
{
    case DayOfWeek.Monday:
    case DayOfWeek.Tuesday:
    case DayOfWeek.Wednesday:
    case DayOfWeek.Thursday:
    case DayOfWeek.Friday:
        return "Not Weekend";

    case DayOfWeek.Saturday:
    case DayOfWeek.Sunday:
        return "Weekend";
        
    default:
        throw new ArgumentOutOfRangeException();
}