1 
public static List<PreviewSchedule> BuildPreviewSchedule(Chatham.Business.Objects.Transaction transaction) { List<PreviewSchedule> items = new List<PreviewSchedule>(); List<ScheduleItem> scheduleItems = new List<ScheduleItem>(transaction.ScheduleCollection.FindAll(row => row.IsDeleted == false)); bool allFromDateFilledIn = !scheduleItems.Exists(item => !item.FromDate.HasValue); bool allFloatingFromDateFilledIn = !scheduleItems.Exists(item => !item.FloatingFromDate.HasValue); scheduleItems.Sort((a, b) => a.FromDate.GetValueOrDefault().CompareTo(b.FromDate.GetValueOrDefault())); scheduleItems.Sort((a, b) => SortIt(a, b, allFromDateFilledIn, allFloatingFromDateFilledIn)); for (int i = 0; i < scheduleItems.Count; i++) { items.Add(new PreviewSchedule { Drop = i == 0 ? "$0.00" : ((scheduleItems[i - 1].PrincipalNotionalAmount - scheduleItems[i].PrincipalNotionalAmount)).Value.ToString(Format.CurrencyCentsIncludedFormatStringDollarSign), EndDate = GetDateOrNull(scheduleItems[i].ToDate), StartDate = GetDateOrNull(scheduleItems[i].FromDate), Notional = scheduleItems[i].PrincipalNotionalAmount.Value.ToString(Format.CurrencyCentsIncludedFormatStringDollarSign), FloatingEndDate = GetDateOrNull(scheduleItems[i].FloatingToDate), FloatingStartDate = GetDateOrNull(scheduleItems[i].FloatingFromDate) }); } return items; }

Here is the method that we call to return our schedule to the front end in our mvc app. Now, this list has been mixing up the last two rows on a specific model the same way each time. Look at the pic: enter image description here

Last two rows of the table, you can obviously see the last two rows are switched around, because the dates don't follow each other. This method is spitting back those mixed up dates, and I'm thinking it's a problem with the sorting. Can any of you guys see where the sorting would cause this?

Thanks ahead of time.

Edit:

SortIt() code:

private static int SortIt( Chatham.Business.Objects.ScheduleItem a, Chatham.Business.Objects.ScheduleItem b, bool allFromDateFilledIn, bool allFloatingFromDateFilledIn) { return SortIt(a.FromDate, a.FloatingFromDate, b.FromDate, b.FloatingFromDate, allFromDateFilledIn, allFloatingFromDateFilledIn); } private static int SortIt(DateTime? aFrom, DateTime? aFloatingFrom, DateTime? bFrom, DateTime? bFloatingFrom, bool allFromDateFilledIn, bool allFloatingFromDateFilledIn) { DateTime? a = null; DateTime? b = null; if (allFromDateFilledIn == false && allFloatingFromDateFilledIn == false) { a = aFrom ?? aFloatingFrom; b = bFrom ?? bFloatingFrom; } else { a = allFromDateFilledIn ? aFrom : aFloatingFrom; b = allFromDateFilledIn ? bFrom : bFloatingFrom; } if (a.HasValue && b.HasValue) return a.Value.CompareTo(b.Value); return 0; }
Improve this question
3
  • It looks like you sort the list twice - the first of which is redundant if you immediately re-sort. What's the method you're using in the second sort? Can you post the code of SortIt? Commented Apr 4, 2011 at 15:08
  • A short example of the data in the scheduleItems input and wanted output could be helpful. Commented Apr 4, 2011 at 15:14
  • Each item in the passed in list is a custom object with lots of properties, the most important ones being from/to dates of payments. the output should sort this list based on those dates, and it's seeming to mix up the last two for some reason. as you can see, start SHOULD pick up where the last one ENDED, but the last two don't match this pattern when the rest of the schedule does. Commented Apr 4, 2011 at 15:18

2 Answers 2

Reset to default
2

I notice the second-to-last row is the only one that has all four dates filled in. I also notice that 01-Oct-2013 is before 01-Nov-2013. I strongly suspect those are the dates being compared together. I can't completely diagnose or correct the issue without knowing what the SortIt method looks like, though. Regardless, that's probably the source of your problem, so I'd focus your efforts there.

Consider what should happen when all four dates are filled in, and figure out how to handle that case.

Edit:

Now that you've added the SortIt code, take a look at your allFromDateFilledIn and allFloatingFromDateFilledIn flags. Both of these are always going to be false with your example data, because both the From and FloatingFrom columns contain at least one null cell somewhere. Therefore, your SortIt method is always going to evaluate this:

a = aFrom ?? aFloatingFrom; b = bFrom ?? bFloatingFrom;

...which means comparing values from different columns together. It also means that when both From and FloatingFrom exist, From always wins as the comparison value.

Edit 2:

You could try replacing the above with an inner if/else like this:

if (aFrom != null && bFrom != null) { a = aFrom; b = bFrom; } else if (aFloatingFrom != null && bFloatingFrom != null) { a = aFloatingFrom; b = bFloatingFrom; } else { a = aFrom ?? aFloatingFrom; b = bFrom ?? bFloatingFrom; }

I feel like maybe that logic could be reduced/prettified, but it seems easiest to understand this way. Note that From still has higher priority than FloatingFrom.

You might want to consider what your boolean flags are doing, as well. They'll only come into play when one or the other column is completely full, in which case they'll lock-in that column as the comparison column. That may be what you want, or it may be unnecessary. You've already established that From takes precedence over FloatingFrom, so without a reason to override that rule, I'd just follow it for the sake of consistency. Just a thought.

Improve this answer
Sign up to request clarification or add additional context in comments.

8 Comments

SortIt() has been posted. But I will start looking into that. Good catch. Let me know if you see anything in SortIt()
I'm convinced you are correct. However, I'm not really sure how to implement a fix for this. Would the fix need to occur in SortIt() or in the method that calls it?
@slandau - I think you could do it in SortIt. Before using the ?? operator, check whether both a and b have a column which is non-null for both of them. If they do, use that. I'll edit.
Yeah I wasn't sure if it was a problem with how the flags were set or something...this way of sorting is new to me, only been a professional for about 5 months! just graduated, lol
@slandau - No worries, looks like you weren't too far off from a solution. Edited, try now.
|
1

There is a problem here:

if (a.HasValue && b.HasValue) return a.Value.CompareTo(b.Value); return 0;

This can give inconsistent return values when either a or b doesn't have a value. Imagine if the sort method calls this with a=2011/04/24 and b=null. It's going to return 0. Later in the same sort, it might be called with a=null and b=2011/03/24. In both cases, the method will return 0.

The behavior of List.Sort when the comparison method returns inconsistent values is undefined. Here you have a case where, given three values (I'll use numbers, but the same will hold true for dates), you can't give a reliable sort.

a = 5 b = 10 c = null

Comparing a and c returns 0. Comparing b and c returns 0, as well. One assumes that if a==c and b==c, then a==b. But in this case a < b. This is going to cause Sort to behave unpredictably. Some sorting methods will go into an infinite loop in this situation, or crash.

Improve this answer

Comments

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.