Is it safe to remove an entry from a Hashtable while iterating?

Question

In other words, is this safe?

Hashtable myDict = ... //fill with some data

foreach (DictionaryEntry pair in myDict)
{
   if (someCondition)
       myDict.Remove(pair.Key);
}

It doesnt seem to have any side effects in my application so far.

edit: i have to mention that in my specific case, this dictionary contains only 1 entry.

edit2: sorry, the datatype is a Hashtable not a Dictionary.

Check here: http://stackoverflow.com/questions/11365725/delete-item-from-dictionary-while-iterating-over-it — Hassan, Apr 17 '14 at 12:33
have you tried running a test sample like that? It will throw an error. Also a `DictionaryEntry` is the wrong type — Jonesopolis, Apr 17 '14 at 12:40
I am sorry, I gave the wrong datatype. it is not a dictionary but a Hashtable — clamp, Apr 17 '14 at 12:56

score 7 · Accepted Answer · answered Apr 17 '14 at 12:40

7

No it is not safe, the contract of IEnumerator specifies that MoveNext should throw an exception if the underlying collection was modified after the enumerator was created.

answered Apr 17 '14 at 12:40

Lee

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score 1 · Answer 2 · answered Apr 17 '14 at 12:43

1

No, it is not safe. with every removed entry it will reduce index no and will move to next element with increasing current index no, so it will create problem there.

answered Apr 17 '14 at 12:43

score 0 · Answer 3 · answered Apr 17 '14 at 12:43

0

@Lee gave you the answer.

It would be safe this way:

var toDelete = myDict.Where(someCondition).ToArray();
foreach (DictionaryEntry pair in toDelete)
    myDict.Remove(pair.Key);

answered Apr 17 '14 at 12:43

vtortola

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Is it safe to remove an entry from a Hashtable while iterating?

3 Answers3