C#•2w ago

Collection was modified. Enumeration operation may not execute.

Code:

public async Task<bool> DeleteFolder(Folder folder) 
{
    if (folder.SubFolders.Any()) 
    {
        foreach (Folder f in folder.SubFolders) 
        {
            await DeleteFolder(f);
        }
    }

    if (folder.Files.Any()) 
    {
        foreach (Core.Domain.Entities.File file in folder.Files) 
        {
            DisconnectAndNullifyMetadataAndSharing(file);
            _db.Files.Remove(file);
        }
    }

    folder.ParentFolder = null;
    folder.ParentFolderId = null;

    DisconnectAndNullifyMetadataAndSharing(folder);
    _db.Folders.Remove(folder);

    return await _db.SaveChangesAsync() > 0;
}

// Utility Function
private void DisconnectAndNullifyMetadataAndSharing(BaseForFileFolder entity) 
{
    if (entity.Metadata != null)
    {
        Metadata metadata = entity.Metadata;
        metadata.File = null;

        entity.Metadata = null;
        entity.MetadataId = null;
    }
    if (entity.Sharing != null)
    {
        Sharing sharing = entity.Sharing;
        sharing.File = null;

        entity.Sharing = null;
        entity.SharingId = null;
    }
}

public async Task<bool> DeleteFolder(Folder folder) 
{
    if (folder.SubFolders.Any()) 
    {
        foreach (Folder f in folder.SubFolders) 
        {
            await DeleteFolder(f);
        }
    }

    if (folder.Files.Any()) 
    {
        foreach (Core.Domain.Entities.File file in folder.Files) 
        {
            DisconnectAndNullifyMetadataAndSharing(file);
            _db.Files.Remove(file);
        }
    }

    folder.ParentFolder = null;
    folder.ParentFolderId = null;

    DisconnectAndNullifyMetadataAndSharing(folder);
    _db.Folders.Remove(folder);

    return await _db.SaveChangesAsync() > 0;
}

// Utility Function
private void DisconnectAndNullifyMetadataAndSharing(BaseForFileFolder entity) 
{
    if (entity.Metadata != null)
    {
        Metadata metadata = entity.Metadata;
        metadata.File = null;

        entity.Metadata = null;
        entity.MetadataId = null;
    }
    if (entity.Sharing != null)
    {
        Sharing sharing = entity.Sharing;
        sharing.File = null;

        entity.Sharing = null;
        entity.SharingId = null;
    }
}

Error:

System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
   at System.Collections.Generic.List`1.Enumerator.MoveNext()
   at CloudStoragePlatform.Infrastructure.Repositories.FoldersRepository.DeleteFolder(Folder folder) in C:\Users\rusha\source\repos\Cloud Storage Platform\CloudStoragePlatform.Infrastructure\Repositories\FoldersRepository.cs:line 135

System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
   at System.Collections.Generic.List`1.Enumerator.MoveNext()
   at CloudStoragePlatform.Infrastructure.Repositories.FoldersRepository.DeleteFolder(Folder folder) in C:\Users\rusha\source\repos\Cloud Storage Platform\CloudStoragePlatform.Infrastructure\Repositories\FoldersRepository.cs:line 135

It seems that the error is being triggered because database is being updated while iterating over the collection of entities in the database or is it happening only because properties of collection are being changed while inside the for loop or because of _db.Folders.Remove(...) ? Also how can I fix it because at the end of the day I want to modify the collection and delete the rows I wanna delete? I got an idea but I think forgot it

12 Replies

surf68•2w ago

presumably it's the call to DeleteFolder while iterating over folder.SubFolders

sibber•2w ago

is that ef core?

MasterSubarashii•2w ago

when you delete "f" inside folder.Subfolders it causes it i guess

sibber•2w ago

you cant modify a collection while enumerating it

!RushaanOP•2w ago

yea

MasterSubarashii•2w ago

just assign folder.Subfolders to another variable and iterate over that while keeping the folders parameter like that

surf68•2w ago

the easy solution would be to iterate over folder.SubFolders.ToList() to bring a copy of the collection into memory

!RushaanOP•2w ago

oh, the line the error is pointing to seems to be the first foreach loop

MasterSubarashii•2w ago

yep like the surf and sibber said

!RushaanOP•2w ago

okay, EF Core will still track the changes right?

surf68•2w ago

yes, you're still operating on the same instances of the subfolder, you're just iterating over a different collection.

!RushaanOP•2w ago

alr imma try it damn it worked tysm imma test it a lil more, yep its fully working

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Collection was modified. Enumeration operation may not execute.