Sorting a list based on date and time

Question

I have a class that is used to basically store samples from data being read from a system. Within that class is a property that I use to store the date and time of that sample:

public class ReadingValue
{
    public DateTime DateTimeOfReading { get; set; }
    public float Reading { get; set; }
}

I need to sort a list of ReadingValue based on the DateTimeOfReading property.

This is what I've come up with:

public IEnumerable<ReadingValue> Hourly(IList<ReadingValue> readings)
{
    var sortedReadings = readings.OrderBy(x => x.DateTimeOfReading.TimeOfDay)
        .OrderBy(x => x.DateTimeOfReading.Date)
        .OrderBy(x => x.DateTimeOfReading.Year);

    return sortedReadings;
}

The code seems to work, when I pass in a list of ReadingValue's it returns the list in sorted order. Is there anything I've overlooked or should do differently? I know time and date programming can be a tricky topic with things like timezones, daylight savings etc. but sorting dates and times shouldn't involve any of that, I don't think.

Answer 1

You should first do OrderBy and then you should do ThenBy instead of doing another OrderBy. What you are currently doing is that you are re-ordering everything after your first OrderBy.

public IEnumerable<ReadingValue> Hourly(IList<ReadingValue> readings)
{
    var sortedReadings = readings.OrderBy(x => x.DateTimeOfReading.TimeOfDay)
        .ThenBy(x => x.DateTimeOfReading.Date)
        .ThenBy(x => x.DateTimeOfReading.Year);

    return sortedReadings;
}

Answer 2

You could simplify it like this -

public IEnumerable<ReadingValue> Hourly(IEnumerable<ReadingValue> readings)
{
    return readings.OrderBy(x => x.DateTimeOfReading);
}

And why is that method called Hourly? Perhaps OrderReadings would be more appropriate.

Answer 3

In addition to @PankajGupta answer I would like to add, that you better should use an IEnumerable<ReadingValue> instead of an IList<ReadingValue> as the methods argument type.

In this way you aren't restricted to pass an IList<> but you can for instance pass any array ReadingValue[], ICollection<ReadingValue> or any object which implements an IEnumerable<ReadingValue>to this method as well.

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Because methodnames should be made out of verbs or verb phrases you should consider to change the methodname from Hourly to SortHourly().

See: NET naming guidelines