Sorted list items

Question

Is it possible to add items to sorted list with the same value, because when I am trying to do so it shows me an error:
"An entry with the same key already exists."
If it's possible, then how?

possible duplicate of [C# Sortable collection which allows duplicate keys](http://stackoverflow.com/questions/5716423/c-sharp-sortable-collection-which-allows-duplicate-keys) — Tim Partridge, Sep 15 '15 at 17:05

sji · Accepted Answer · 2015-09-16T09:59:27.667

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It is not possible* to add duplicate keys as stated by other users.

In c# you might be able to use the Lookup class instead, which allows multiple values to be stored with the same key.

See: http://msdn.microsoft.com/en-us/library/bb460184.aspx

* It is possible, see comments, but only by defining a comparitor that never returns equality for equal items, which IMO is a really really bad idea.

edited Sep 16 '15 at 09:59

answered Mar 12 '12 at 10:13

sji

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It's possible. See [Knasterbax's answer](http://stackoverflow.com/a/21886340/224976) to a similar question – Tim Partridge Sep 15 '15 at 17:03
That solution breaks a precondition of the container (that two equal keys will return equality), and as commenters have pointed out that introduces a raft of other problems. Best to use the container intended for use in this fashion IMO. That said I will update my answer. – sji Sep 16 '15 at 09:55
Good point. The comments in Kasterbax's answer reveal some caveats – Tim Partridge Oct 15 '15 at 14:49

score 1 · Answer 2 · answered Mar 12 '12 at 10:07

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No, it's not possible. The keys must be unique.

answered Mar 12 '12 at 10:07

Andrew Cooper

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It's possible. See [Knasterbax's answer](http://stackoverflow.com/a/21886340/224976) to a similar question – Tim Partridge Sep 15 '15 at 17:03
Using Kasterbax's answer has caveats. Read the comments – Tim Partridge Oct 15 '15 at 14:49

score 0 · Answer 3 · edited May 23 '17 at 10:34

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Define a class that implements IComparer. When you instantiate the SortedList, you pass in an instance of your class. Check out Knasterbax's answer.

edited May 23 '17 at 10:34

Community

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answered Sep 15 '15 at 17:01

Tim Partridge

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score 0 · Answer 4 · answered Mar 12 '12 at 10:11

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Key should be unique. See this in MSDN

ArgumentException   - An element with the specified key already exists in the SortedList object.

http://msdn.microsoft.com/en-us/library/system.collections.sortedlist.add.aspx

answered Mar 12 '12 at 10:11

PraveenVenu

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It's possible. See [Knasterbax's answer](http://stackoverflow.com/a/21886340/224976) to a similar question – Tim Partridge Sep 15 '15 at 17:03

Sorted list items

4 Answers4