Question

I have a method that returns the past x days and it currently does the following:

var dates = new List<DateTime>();

for (int i = 0; i < numDays; i++)
{
    dates.Add(DateTime.Today.AddDays(-i));
}

return dates;

I feel like there should be a more compact way of doing this, perhaps using LINQ. Suggestions? Also, if I do keep it the way I have it, is DateTime.Today such that this would be more efficient if I stored it in a variable outside the loop and then called AddDays on that value within the loop?

Edit: LINQ uses lazy evaluation, right? I’m getting crazy images in my head:

return DateTime.AllDaysInTheHistoryOfTimeEver.Where(day =>
    day.BeforeOrOn(DateTime.Today) &&
    day.After(DateTime.Today.AddDays(-numDays))
);

Answer 1

var start = DateTime.Today;
var days = Enumerable.Range(0, numDays).Select(i => start.AddDays(-i)).ToList();

Capturing start first avoids a corner-case of running it at around midnight.