public int Calculate(DateTime start, DateTime end, DurationFormatTypes format)
        {
            switch (format)
            {
                case DurationFormatTypes.Days:
                default:
                    //TODO: more complicated logic to calculate duration.
                    //do not calculate free days (holidays, weekends etc.);
                    var time = end - start;
                    var duration = time.Hours + (time.Days * _workdayLength);
                    if (time.Minutes > 30)
                    {
                        duration++;
                    }

                    return duration;
                    break;

            }
        }
        /// <summary>
        /// Defines how to display duration.
        /// It can be configure to display hours, days etc. depending on durationFOrmat.
        /// </summary>
        public void InitialiseDurationFormat(DurationFormatTypes durationFormat)
        {
            _view.DurationColumn.AspectGetter =
                (obj) =>
                {
                    var workItem = (obj as WorkItem);
                    if (workItem != null)
                    {
                        int duration = 0;
                        foreach (var comment in workItem.Comments)
                        {
                            duration += _durationCalculator.Calculate(comment.StartTime, comment.EndTime, durationFormat);
                        }

                        return duration;
                    }

                    return string.Empty;
                };
        }