I thought that this question C# newbie List question was a duplicate (sorry, as a noob meta user I can only post one link, please follow my comment on that question), but other folks don't seem to agree.

If two questions are phrased differently, but describe the same underlying problem (and therefore have the same answers) are they not same question?

Thanks, from a puzzled Binary Worrier :(


  • 7
    When it's ajar? Commented Aug 4, 2009 at 18:18
  • 1
    @gnostradamus awesome. I have always loved that crappy childrens' pun. Commented Aug 4, 2009 at 22:11
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    Possible duplicate of Closing as Duplicate When the Answers are Duplicates ;-) Of course, the accepted answers are 180 degrees from each other, so maybe not. If the same question is asked and gets two opposite answers, is it a duplicate? There's a koan in here somewhere, I'm sure of it!
    – Ed Staub
    Commented Nov 7, 2012 at 15:41
  • What is the sound of a unique duplicate? Consider well, grasshopper. Commented Apr 28, 2013 at 13:06

6 Answers 6


Rule of thumb: If you ask a question similar to another question and it is likely to get the exact same answer, you have yourself a duplicate question.

In your case, take the opposite of that. If the question is similar and it is likely to NOT get the exact same answer, you likely do not have a duplicate.

  • TheTXI: I would also apply that rule of thumb, and thought I had done so in this instance. Commented Aug 4, 2009 at 16:53
  • I can't speak for the entire community and I am sure others have their own criteria and some also have more of a trigger finger than others.
    – TheTXI
    Commented Aug 4, 2009 at 16:56
  • This is a good rule of thumb. Doesn't matter how fancy you get phrasing your question, if it boils down to looking for an answer that's already been provided for a similar question, then you've got no reason to argue.
    – Shog9
    Commented Aug 4, 2009 at 17:07
  • Poor TheTXI you got -1. Thanks for helping in test, +10 ;)
    – akarnokd
    Commented Aug 4, 2009 at 17:10
  • kd304: Thanks for the effort, but I was over my rep limit anyway, so the -2 can't be made up with your upvote :)
    – TheTXI
    Commented Aug 4, 2009 at 17:13
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    I'm not sure I agree with this rule of thumb... meta.stackexchange.com/questions/95799/… Commented Jun 29, 2011 at 21:52
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    @TheTXI: What if the questions are asking two different things that could have one common answer, even though the original question's answer doesn't mention what the second question is asking?
    – jvriesem
    Commented Aug 14, 2015 at 3:14

Other example to consider: duplicating a dead/badly asked question

If you have someone coming and asking a question, but not putting effort in it, not providing feedback or details, this question will most likely get downvoted in the end, and forgotten.

Now what if a new user comes, and has the same problem? He searches for existing questions on the site, and finds a very similar one. However, he doesn't own the question, he can't add details to it, all he could do is post a new answer (leading to the many "i have the same problem" answers, which are sometime useful, with new details, but which shouldn't be answers).

In this case, I think he should ask it as a new question, giving his own details. This new question should contain information about the duplicate (to prevent fast people from closing it after a fast search), something like:

I have searched for duplicate, and found this question (link here). However, this question is abandoned, mostly because the author didn't provide any feedback on his problem.

In this case, the original question should be the one closed for duplicate, and point to this new one. Because we can't let someone "ruin" a problem and prevent others, more motivated, to find a solution.

This particular case of duplicate would help improving the quality of answers on the sites.

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    well if the question is extra-crappy it should be flagged for straight deletion. Commented Jan 20, 2010 at 10:46

If they're phrased very differently, I'd leave them both open. It casts the net wider. Obviously two people seeking the same answer asked two very differently-phrased questions. If you kill one of the questions, you effectively prevent 50% of the potential users from getting their answer in the future simply because they didn't ask the question the way the other 50% of users did.

In instances like this, I will cross-reference each question as an answer, or a comment.

  • 2
    But in Closing a question, you're not automatically deleting it. If Some one find the closed question, it'll have a great big "Duplicate of [link]" banner if they follow the link they'll get the correct answer. Closed <> Deleted Commented Aug 4, 2009 at 16:52
  • Ideally, you'd have a whole bunch of closed duplicates, each asked in a different way, and all linking back to The One True Question that gives the answer...
    – Shog9
    Commented Aug 4, 2009 at 18:15
  • So, what happens if I ask "How do I do X in C#?", Jon Skeet gives a great answer, and somebody noticed that somebody asked the exact same question when Jon was on vacation? Which should be the duplicate? Commented Aug 4, 2009 at 21:19
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    @David: if they're the exact same question and both have good answers, then ask a moderator to merge them.
    – Shog9
    Commented Aug 5, 2009 at 16:17
  • @Shog9 what is the merge process? Do moderators use it now? Commented Jun 9, 2013 at 18:18
  • Merging moves all the answers from one question to another, then locks the source, @Michael. It's used occasionally.
    – Shog9
    Commented Jun 9, 2013 at 18:20
  • Is it very manual work? I expect single question with merged answers would be much better, than keep separate duplicated questions. Commented Jun 9, 2013 at 18:26
  • As long as a closed/duplicate question remains undeleted, it's a trail marker for future users, that leads them to either the answer to their problem or a place to provide an answer that deals with a slight variation to a theme. Either way, the duplicate serves well when closed.
    – Mogsdad
    Commented Mar 20, 2016 at 16:27

A duplicate is not a duplicate when they are not seeking or asking the exact same thing as something else that already exists.

I don't believe that similar will always be a duplicate, but it can be.

I find it best for authors to highlight similarities between their issue and others, but take it a step further by explaining exactly what they need. This adds distinction between posts...

  • Your putting responsibility on askers to do lots of work, I've seen questions with almost exactly the same title, that would have been listed on the Ask Question page, but that noob (or lazy) users ask anyway. Dups are always going to happen, we need a better way to deal with them. Commented Aug 5, 2009 at 8:16
  • @Binary: who the heck should have the burden in making sure their question is not a dupe? It is 100% on the asker. You mist have missed the ther threads on this very topic which would force newer users to search a bit more fOr their need first. So since this is obviously a dupe now, are you lazy or a noob?
    – RSolberg
    Commented Aug 5, 2009 at 15:35
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    @RSolberg: Neither, I'm just dumb :) I agree with you (honestly) it is the askers responsibility, however, that I asked a duplicate PROOVES my point. I ALWAYS look for dups before asking a question, however, obviously my searches and key words didn't throw up any of the many duplicates of this question. I think it is the askers responsibility, but regardless of how well they look (or don't look at all) before asking, there will be dups. My point is, as a community, we need better mechanisms to deal with duplicates. Yours, Dumb-ary Worrier :) Commented Aug 7, 2009 at 12:49

I think that C# newbie List<Interface> question is a duplicate, but not a duplicate of Why is this cast not possible?.

They are both "why doesn't variance work the way I'd like it to work in C#" duplicates. However, "newbie" is so much simpler that, if it were not a duplicate of many others, it would deserve to stand on its own.

The problem will be finding the other duplicates. The following are from the first page of https://stackoverflow.com/search?q=contravariance+interface+c%23+list+generic. There are ten pages:

BTW, I chose "contravariance" in the above search because I thought there would be fewer occurrences of that word than of "covariance". There were ten pages of each.

  • I'm starting to wonder if it doesn't make more sense to close the older ones as duplicates of the new one. It's the most clear and straight-forward of the lot...
    – Shog9
    Commented Aug 4, 2009 at 18:37
  • Could be. It might also want to become part of the "C# FAQ". Commented Aug 4, 2009 at 19:09

One interesting example today (for C++) was somebody asking how to call a constructor manually and build an object on already allocated space. There was a bit of discussion on whether it was a duplicate of "what does placement new do?", since the questions are within easy grammatical transformations of being answers for each other.

  • In some cases I think that indicates the original question needs new keywords in its subject and/or new tags.
    – Zan Lynx
    Commented Apr 30, 2011 at 1:12

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