Linq to NHibernate - The method Cos is not implemented

Question

In Linq to NHibernate I'm trying to return businesses within a certain distance of a user. Here is what I have so far:

var query = from b in ActiveRecordLinq.AsQueryable<Business>()
                        where (3959 * Math.Acos(Math.Cos((Math.PI * coordinates.Latitude / 180)) * Math.Cos((Math.PI * b.Latitude / 180))
                            * Math.Cos((Math.PI * b.Longitude / 180) - (Math.PI * coordinates.Longitude / 180))
                            + Math.Sin((Math.PI * coordinates.Latitude / 180)) * Math.Sin((Math.PI * b.Latitude / 180)))) <= radiusInMiles
                        orderby b.Name ascending
                        select b;
            return query.ToList();

Unfortunately, it seems that the C# Math class isn't supported in Linq to NHibernate so it gives me the following error:

The method Cos is not implemented

How would I get around this?

Thanks! Justin

Answer 1

You can't use arbitrary .Net functions in server-side Linq queries.

You can use server-side functions with HQL.

Answer 2

You can do three things:

1. Implement it and submit a patch to NHibernate so that everybody can use your implementation
2. Create a failing unit test that isolates the problem and submit it to NHibernate Jira and wait until somebody else implements it.
3. Do not use Linq, but plain old sql or mixed hql for this query.

You will make some people happy when you choose option 1.