gistfile1.cs

var mapping = 
    from periodControl in tariffAndLoadControlLocalType.PeriodControl
    let periodControlType = periodControl.PeriodControlType
    let exceptionDayKey = (int)GetExceptionDayKey(periodControlType)
    let exceptionDay = ExceptionDays(periodControl)
    let periods = 
        from period in periodControl.Period
        let blockId = (int)GetBlockId(periodControlType, period.PeriodType)
        let dictionary = Get(period)
        let workingDays = dictionary.ContainsKey(WorkingDay)
                        ? dictionary[WorkingDay]
                        : new List<PeriodShiftModel>()
        let nonWorkingDays = dictionary.ContainsKey(NonWorkingDay)
                            ? dictionary[NonWorkingDay]
                            : new List<PeriodShiftModel>()
        let block = new TariffAndLoadControlBlock(period.Month, period.Day, workingDays, nonWorkingDays)
        select new { Key = blockId, Value = block }
    select new 
    { 
        Periods = periods, 
        ExceptionDayKey = exceptionDayKey, 
        ExceptionDay = exceptionDay 
    };

var blocks = mapping.SelectMany(x => x.Periods).ToDictionary(x => x.Key, x => x.Value);                
var exceptionDays = mapping.ToDictionary(x => x.ExceptionDayKey, x => x.ExceptionDay);