Many things.
It could be that if you have an
it does not have a field named Id or id. I do not know the .net driver so I am not too sure. In particular, what is the value of item.Id?
If item.Id equals _id, then you probably have a type mismatch. It looks like you tried to avoid that with
but you ignore this type conversion by querying with id in
It could potentially work if you use the variable objectId rather than id.