Nhibernate filtering by user defined function output

Question

I\'m reasonably new to NHibernate and everything has been going pretty well so far but I\'ve come across a problem I\'m not exactly sure of how to go about solving. Basicall

Answer 1

Creating custom dialect extensions is rather easy:

public class CustomFunctionsMsSql2005Dialect : MsSql2005Dialect 
{ 
   public CustomFunctionsMsSql2005Dialect() 
   { 
      RegisterFunction("calculatedistance",
                       new SQLFunctionTemplate(NHibernateUtil.Int32,
                                               "CalculateDistance(?1, ?2, ?3, ?4)"));
   }
}

Register it, like so:

<property name="hibernate.dialect">
  CustomFunctionsMsSql2005Dialect, MyAssembly
</property>

Now you can use it like any other HQL function in queries like those created with session.CreateQuery().

Answer 2

You could use SQL expression in your hibernate queries. Assuming you've mapped a Store type you could write the following query:

var result = session
    .CreateCriteria<Store>()
    .Add(Expression.Sql(
        "dbo.CalculateDistance({alias}.Latitude, {alias}.Longitude, ?, ?) < ?",
        new object[] { 
            -118.4104684d, 
            34.1030032d, 
            100 
        },
        new IType[] { 
            NHibernateUtil.Double, 
            NHibernateUtil.Double, 
            NHibernateUtil.Int32 
        }
    ))
    .List<Store>();