Re: CBS_SORT / LBS_SORT, what algorithm?

Hello ReyesP,

I just get the product group's suggestion on this issue. They also suggest maintaining the sort outside the ComboBox/ListBox control and populate the result to ComboBox/ListBox without SBC_SORT. (They call this as "virtual listbox")

Inside ComboBox, it always uses "Insertion Sort" when SBC_SORT is specified, and a re-sort + re-add of the whole list is also done internally when users add / edit the list items. Insertion sort is a simple sorting algorithm: http://en.wikipedia.org/wiki/Insertion_sort. It is much less efficient on large lists than more advanced algorithms such as quicksort, heapsort, or merge sort. http://en.wikipedia.org/wiki/Sorting_algorithm. In other words, the default implementation of sort in ComboBox does not very fit a large collection of data. Regarding your performance concerns when manually maintaining the sort outside the control, the product group and I compose the following analysis for your reference:

1. We can have a better choice of the sort algorithm according to the operation (insert/update) and the features of the data collection.

For the initial list population, external sorting would be the faster way of doing it since one would likely choose a better sort algorithm than insertion sort. For the incremental update case, doing the lookup/insertion yourself vs. having the control do it wouldn't be any faster if the control did it for you because it's going to be an insertion sort.

2. Benefit of virtual listbox

Virtual listboxes are the way to go since we never insert into the controls but just reflect an external store that likely has an inherent sorting maintained (like a database index, a tree, etc.).

3. We may reuse the sort result in multiple controls.

In this case, we need to display the sort result in two controls: a tree control and a ComboBox control. Instead of sorting twice, we can maintain the sort in one place and simply populate the sort result to the two controls. This can not only ensure that the sort results in both controls are identical, but also improve the overall performance.

ReyesP, is the above info useful to you? Please let me know if you have any concerns or questions. I will spare no effort to help you.

Have a nice weekend!

Best Regards,
Jialiang Ge
Microsoft Online Community Support

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""Jialiang Ge [MSFT]"" <jialge@xxxxxxxxxxxxxxxxxxxx> wrote in message news:0vKuceaNJHA.4468@xxxxxxxxxxxxxxxxxxxxxxxxx
Good morning ReyesP. Welcome to Microsoft Newsgroup Support service! My
name is Jialiang Ge [MSFT]. It's my pleasure to work with you on this issue.

I understand your concerns that overriding sorting with "Owner-Drawn"
causes the ComboBox to lose Accessibility functionality. I also understand
the underlying performance issues if we pre-sort the ComboBox items.
ReyesP, please give me some time. I have conveyed your request to the
product group and am waiting for their suggestions.

To be honest, even if the product group agrees to tell the algorithm of
CBS_SORT in this community, I personally do not suggest programming against
the algorithm because this kind of undocumented implementation may change
in future releases. I have spent several hours on this issue to look for
other more reliable solutions/workarounds. Although I do not have findings
today, I will continue researching with all efforts. Thank you for you
understanding.

Regards,
Jialiang Ge (jialge@xxxxxxxxxxxxxxxxxxxx, remove 'online.')
Microsoft Online Community Support

Delighting our customers is our #1 priority. We welcome your comments and
suggestions about how we can improve the support we provide to you. Please
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msdnmg@xxxxxxxxxxxxxx

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