>>>I have this:
>>>
>>>

>>>
>>>var query = from g in root.Groups
>>>            from r in g.Rules
>>>            from c in r.Conditions
>>>            from a in c.Actions
>>>            where g.Rules != null
>>>            where r.Conditions != null
>>>            where c.Actions != null
>>>            where a.ActionID == ActionId
>>>            select a;
>>>
>>>List<RuleAction> items = query.ToList();
>>>RetVal = items[0];

>>>
>>>
>>>It fails on the last line with "Object reference not set to an instance of an object" because the query returned no results.
>>>
>>>How do I test for this before attempting to convert the results to a list?
>>
>>Test the items for zero length? Maybe:

>>
>>RetVal = items.Count==0 ? null : items[0];

>
>It's failing on this line:
>

>List<RuleAction> items = query.ToList();
>

Not sure I've understood the underlying structure correctly but you might try something like this instead:

Action a = (from x in context.Actions
                         .Include("Condition.Rule.Group.root")
                        where x.Id == ActionId
                        select x).FirstOrDefault();