> Was just talking about this with Robert and I may have misunderstood your
> question.  You may have hit this bug (which has been fixed for a little
> while): https://jira.mongodb.org/browse/CSHARP-418.  What version of the
> driver are using?

> On Thursday, October 4, 2012 8:46:15 AM UTC-5, craiggwilson wrote:

>> You need to access the collection using the base class and then us OfType
>> to add the type restriction.

>> Colleciton<Element>.AsQueryable().OfType<Survey>().Where(f => f.Id == id);

>> On Thursday, October 4, 2012 6:02:21 AM UTC-5, Christian Sparre wrote:

>>> I have a base class *Element *and a subclass *Survey*

>>> In simple form they look like this :)

>>> Element
>>> {
>>>   Guid Id;
>>> }

>>> Survey : Element
>>> {
>>>   String Title;
>>> }

>>> The *Guid Id* is represented as a string in the database using the
>>> [BsonRepresentation(BsonType.String)] attribute

>>> When I save documents and return them all (FindAll) everything works
>>> fine and they are serialized and deserialized as expected.

>>> But when I try to do the following it fails with the error *"Unable to
>>> determine the serialization information for the expression: f.Id"*

>>> Collection<*Survey*>.AsQueryalble().Where(f=>f.Id == id)

>>> But if I query only on the base class *Element*

>>> Collection<*Element*>.AsQueryalble().Where(f=>f.Id == id) it works as
>>> expected.

>>> I have no class maps created manually, and when I lookup the *Survey *class
>>> map the *Id *property seems to be mapped correctly with the string
>>> representation

>>> Any idea?, I know there was a problem with inherited properties and
>>> querying, but that was a long time ago. Also before I changed the
>>> representation to string I had no problems.

>>> --
>>> Christian