I’m new to C# and This is the first time I’m using LINQ queries. I have a Dictionary as Dictionary<(int MeterId, DateTime TimeStamp), float> With data as follows,

<(10411, 12/1/2022 12:30:00 AM), 5700>
<(10411, 13/1/2022 12:30:00 AM), 5200>
<(10412, 12/1/2022 12:30:00 AM), 200>

Then there’s a method to add them to a list with meterId and average value for each day of week. I’m using LINQ queries to calculate the averages and get them to a list.

        public static List<AveragedMeter> CalculateAverageValues(Dictionary<(int MeterId, DateTime TimeStamp), float> groupedMeterValues)
        {
            var lstResult = groupedMeterValues
                .GroupBy(m => new { m.Key.MeterId, m.Key.TimeStamp.DayOfWeek })
                .Select(g => new AveragedMeter
                {
                    MeterId = g.Key.MeterId,
                    AverageMondayValue,
                    AverageTuesdayValue,
                    AverageWednesdayValue,
                    AverageThursdayValue,
                    AverageFridayValue,
                    AverageSaturdayValue,
                    AverageSundayValue
                })
                .ToList();

            return lstResult;
        }

I’m not certain how to get for these average values. My AveragedMeter class is as follows,

    class AveragedMeter
    {
        public int MeterId { get; set; }
        public float AverageMondayValue { get; set; }
        public float AverageTuesdayValue { get; set; }
        public float AverageWednesdayValue { get; set; }
        public float AverageThursdayValue { get; set; }
        public float AverageFridayValue { get; set; }
        public float AverageSaturdayValue { get; set; }
        public float AverageSundayValue { get; set; }
    }

>Solution :

You could filter the data by DayOfWeek inside your select instead of grouping the dictionary, something like this:

static List<AveragedMeter> CalculateAverageValues(Dictionary<(int MeterId, DateTime TimeStamp), float> groupedMeterValues)
{
    var lstResult = groupedMeterValues
        .GroupBy(m => m.Key.MeterId)
        .Select(g => new AveragedMeter
        {
            MeterId = g.Key,
            AverageMondayValue = g.Where(n => n.Key.TimeStamp.DayOfWeek == DayOfWeek.Monday).Average(n => n.Value),
            AverageTuesdayValue = g.Where(n => n.Key.TimeStamp.DayOfWeek == DayOfWeek.Tuesday).Average(n => n.Value),
            AverageWednesdayValue = g.Where(n => n.Key.TimeStamp.DayOfWeek == DayOfWeek.Wednesday).Average(n => n.Value),
            AverageThursdayValue = g.Where(n => n.Key.TimeStamp.DayOfWeek == DayOfWeek.Thursday).Average(n => n.Value),
            AverageFridayValue = g.Where(n => n.Key.TimeStamp.DayOfWeek == DayOfWeek.Friday).Average(n => n.Value),
            AverageSaturdayValue = g.Where(n => n.Key.TimeStamp.DayOfWeek == DayOfWeek.Saturday).Average(n => n.Value),
            AverageSundayValue = g.Where(n => n.Key.TimeStamp.DayOfWeek == DayOfWeek.Sunday).Average(n => n.Value),         
        })
        .ToList();

    return lstResult;
}