Why did you close my article about the custom combobox for aspnet?

This isn't the right place to ask - you probably want Sugs and Bugs[^] or Article Writing[^] as the admins read them, and can look at the article in question.

But as one of those who can help to approve articles let me explain the process:

1) You write an article and submit it.
2) It goes into a pending list, visible only to those with approval authority (which is just the appropriate rep points in the Organiser category).
3) It is read, and voted on. 5 "Approve" votes and it's through, 5 "Not approve" votes and it isn't - normally, you will receive an email to explain why.

There are loads of reasons why an article may not get approved - it may be too basic, it may be unclear, it may just need re-formatting - and there are voting categories for each of these.
It could also be spam, plagiarised or abusive - these are "quick close" reports, which will normally affect your account rep as well.

I didn't see your article, so I can't comment in this case, but it's not as simple as "why did you close it?" - it normally takes a number of votes one way or the other before it leaves the pending queue. (Although admins can close it immediately if they so desire - but they only use this for flagrant abuse)