Thanks for the update - glad you've got it sorted :). Collection sync
is always a pain...
I've just started testing a custom AutoMapper IObjectMapper
implementation which does a full model collection <-- --> entity
collection sync; if anyone's interested in giving feedback or
improvements then drop me a note. It's currently at a very primitive
stage, but works for basic scenarios and allows code such as
return this.WorkUnit.Execute( (session, context) => {
var entity = session.Get<Entity>(model.Id);
if(entity == null) context.Fail(...);
return context.Map(model, entity);
// Entire object graph gets synced here
})
/Pete
From: [email protected] [mailto:[email protected]] On
Behalf Of Matteo Migliore
Sent: 09 July 2013 14:25
To: [email protected]
Subject: Re: [nhusers] Modify the collections of an entity "collection
was modified" exception
I found the issue, it was because I did the mapping from the DTO
(command) to the entity.
In a child entity there was a navigation property to the parent that
came from the mapping (AutoMapper) instead that from the loaded entity
from the session. So the Child.Parent instance was different from "var
parent = Session.Load(id)" instance.
This situation caused the problem. Now I copied the loaded instance in
the child property and everything works.
P.S.
So the Synchronize method is correct, is possible to use it.
Thanks!
On Friday, July 5, 2013 3:34:13 PM UTC+2, Matteo Migliore wrote:
Hi Pete,
I completely agree, clonin is just a patch, but I placed ToArray
everywhere and the problem persists.
I also wrote a unit test and with not lazy collection everything works
fine.
I've the exception when I call Session.Merge, and the StackTrace does
not contain nothing,
also without "Just my code" enabled.
I really cannot understand the problem and how to reproduce it in a unit
test.
On Fri, Jul 5, 2013 at 12:03 PM, Pete Appleton
<[email protected]> wrote:
> Cloning is definitely the wrong solution IMO, the underlying issue is
exactly what the exception message says. My original code assumed that
'toRemove' was the collection that was getting modified during
iteration, but clearly I'm wrong if it didn't work. Best suggestion for
you is to carefully work through the exception stack trace to find out
which collection is the problem; once you've found that, then use the
ToList() / ToArray() technique. NB, you may find it helpful to untick
the 'Just my code' option in the VS debugger options.
>
> /Pete
>
> -----Original Message-----
> From: [email protected] on behalf of Matteo Migliore
> Sent: Thu 7/4/2013 4:49 PM
> To: [email protected]
> Subject: Re: [nhusers] Modify the collections of an entity "collection
was modified" exception
>
> Chris, Pete
>
> the ToDictionary is not deferred exactly the ToList and ToArray,
> so for me is not needed to do anything more.
>
> Instead the clone of the entity works, but I don't like it, because
the collections
> are modified also if not necessary.
>
> Idea? :)
>
> Thanks!
> Matteo
>
> On Thursday, July 4, 2013 5:11:30 PM UTC+2, PeteA wrote:
>
> Change
> var toRemove = firstCollection.Where(item =>
secondCollection.All(x => x.Key != item.Key));
> to
> var toRemove = firstCollection.Where(item =>
secondCollection.All(x => x.Key != item.Key)).ToArray();
>
> As it stands, your code is lazily iterating toRemove; as soon
as something's removed from it, you'll get exception you described.
This is not related to NHibernate, it's a standard 'feature' of .NET :).
>
> /Pete
>
> -----Original Message-----
> From: [email protected] <javascript:> on behalf of
Matteo Migliore
> Sent: Thu 7/4/2013 11:58 AM
> To: [email protected] <javascript:>
> Subject: [nhusers] Modify the collections of an entity
"collection was modified" exception
>
> Hi,
>
> I obtain the error "Collection was modified; enumeration
operation may not execute." when I try to save (merge)
> a loaded entity.
>
> I use AutoMapper to write the values from the DTO (command) to
the loaded entity and this method to synchronize
> the collection between the entity and the command:
>
> public static ICollection<TFirst> Synchronize<TFirst,
TSecond>(
> this ICollection<TFirst> first,
> IEnumerable<TSecond> second,
> Func<TSecond, TFirst> convert = null,
> Func<TFirst, int> firstHash = null,
> Func<TSecond, int> secondHash = null)
> {
> if (firstHash == null)
> {
> firstHash = x => x.GetHashCode();
> }
>
> if (secondHash == null)
> {
> secondHash = x => x.GetHashCode();
> }
>
> if (convert == null)
> {
> convert = x => Mapper.Map<TFirst>(x);
> }
>
> var firstCollection = first.ToDictionary(x =>
firstHash(x), x => x);
> var secondCollection = second.ToDictionary(x =>
secondHash(x), x => x);
>
> var toAdd = secondCollection.Where(item =>
firstCollection.All(x => x.Key != item.Key)).Select(x =>
convert(x.Value));
>
> foreach (var item in toAdd)
> {
> first.Add(item);
> }
>
> var toRemove = firstCollection.Where(item =>
secondCollection.All(x => x.Key != item.Key));
>
> foreach (var item in toRemove)
> {
> first.Remove(item.Value);
> }
>
> return first;
> }
>
> How can I fix the problem?
>
> Thanks,
> Matteo
>
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