C#•3y ago

❔ why is .ToList() considered being in a right answer for this problem?

https://stackoverflow.com/questions/604831/collection-was-modified-enumeration-operation-may-not-execute/

Stack Overflow

Collection was modified; enumeration operation may not execute

I can't get to the bottom of this error, because when the debugger is attached, it does not seem to occur.

Collection was modified; enumeration operation may not execute

Below is the code.
This i...

ero•7/28/23, 11:19 AM

You linked an answer which says ToList isn't the right answer?

Moods•7/28/23, 11:21 AM

The most-voted answer also explained why

Moods•7/28/23, 11:21 AM

deprecatio•7/28/23, 11:55 AM

yeah ToList would be a copy of the object for that thread
but that's not a great solution because it could lead to a lot of copies and a lot of memory
maybe a concurrent dictionary would be better
or a lock
or a soft delete
it depends
the immutable thing could also be good, a more formal approach

Eero You linked an answer which says ToList *isn't* the right answer?

MechnoOP•7/28/23, 12:41 PM

Sorry i meant the answer with green check

MMoods The most-voted answer also explained why

MechnoOP•7/28/23, 12:42 PM

By tolist isnt thread safe or is it?

MechnoOP•7/28/23, 12:43 PM

The other thread could change the list while tolist is executing on other thread

MechnoOP•7/28/23, 12:53 PM

It just doesnt feel right that people would just go with that answer or maybe there is something that i am missing

deprecatio•7/28/23, 2:41 PM

you can look at the source of ToList() by F12 it
answer is 99% it's not therad safe

MMechno By tolist isnt thread safe or is it?

Moods•7/28/23, 7:37 PM

i see what u mean

Moods•7/28/23, 7:38 PM

ig you'd have to make it Immutable

Moods•7/28/23, 7:38 PM

https://stackoverflow.com/a/57799537 okay this answer then

Stack Overflow

Collection was modified; enumeration operation may not execute

MMoods ig you'd have to make it Immutable

MechnoOP•7/28/23, 8:20 PM

but you can still call both methods at the same time which mean u you can access the 'subscribers' twice at the same time. Once when you are replacing it with new collection and second time when I guess foreach is getting reference to it?

deprecatio•7/29/23, 11:01 AM

making the object immutable means that you can't write it so there could not be a shared writing error
but yeah still all the other parts are not protected for thread-safeness

Accord•7/30/23, 11:19 AM

Was this issue resolved? If so, run

/close

/close

otherwise I will mark this as stale and this post will be archived until there is new activity.

❔ why is .ToList() considered being in a right answer for this problem?

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