Remove an element while enumerating through a collection

[Edward Diener]

If I am enumerating through a collection, will removing the entry which is
my current one destroy my ability to keep enumerating the remaining elements
successfully. In my case the collection is a hybrid dictionary and while I
am enumerating the elements I want to remove the current one depending on
its value. Of course I know the technique of keeping a list of keys in a
separate array, to remove the appropriate ones after my enumeration has
finished, but I would like to know if this is necessary with .NET
collections or if I can remove while I am enumerating instead..

 

[Mattias Sjögren]

Edward,

or if I can remove while I am enumerating instead..

No you can't.



Mattias

 

[Alvin Bruney [MVP]]

Actually, you can.

foreach(ListItem li in new Array(IteratingCollection)
{
if(li.Selected)
li.Remove();
}

roughly

--
Regards,
Alvin Bruney [MVP ASP.NET]

[Shameless Author plug]
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[Edward Diener]

Actually, you can.

foreach(ListItem li in new Array(IteratingCollection)
{
if(li.Selected)
li.Remove();
}

Huh ! What in the world is this doing ? How does li.Remove remove an item
from my original collection ?

 

[Andy Fish]

Mattias is right - have a look here if you want it written in black and
white.

http://msdn.microsoft.com/library/d...lrfsystemcollectionsienumeratorclasstopic.asp

"An enumerator remains valid as long as the collection remains unchanged. If
changes are made to the collection, such as adding, modifying or deleting
elements, the enumerator is irrecoverably invalidated and the next call to
MoveNext or Reset throws an InvalidOperationException."

 

[Giedrius]

Actuall'y you can write your custom Collection with custom Enumerator. And
use any logic you want.