Question

Assume that the class Data is defined as {DateTime TransactionDate, int ItemCount}.
I get an original IEnumerable containing scattered TransactionDates and ItemCounts and I need to write a method that returns a collection with all the days filled in between the minimum and the maximum days in the original collection.

For instance, if I get:
12/5/2009 15.00
12/7/2009 10.00
12/10/2009 75.00

I need to generate something like this:
12/5/2009 15.00
12/6/2009 0.00
12/7/2009 10.00
12/8/2009 0.00
12/9/2009 0.00
12/10/2009 75.00

Get you give me an elegant way of doing this with c# 3.0?

I have a list of all dates between the minimum and maximum dates. So I assume all I have to do is “foreach” the intersect collection (allDates-existingDates) and insert a new element for each of these. Am I right?

Thanks

Answer 1

Here’s an extension method that should do the job. It’s purely based on iterators (IEnumerable<Data>), so it would seem quite a nice approach to me.

public static IEnumerable<Data> FillIn(this IEnumerable<Data> original)
{
    Data lastItem = null;
    foreach (var item in original)
    {
        if (lastItem != null)
        {
            var fakeItem = new DateTime(lastItem.TransactionDate.Year,
                lastItem.TransactionDate.Month, lastItem.TransactionDate.Day)
                .AddDays(1);
            while (fakeItem.TransactionDate != item.TransactionDate)
            {
                yield return fakeItem;
                fakeItem.TransactionDate = fakeItem.TransactionDate.AddDays(1);
            }
        }
        lastItem = item;
        yield return item;
    }
}

Where Data is simply defined as:

class Data
{
    public DateTime TransactionDate;
    public int ItemCount;
}