Nhibernate QueryOver by Enum Flags

Question

I have a query by QueryOver :

public IList<Person> SearchTest(PersonEnumType type)
{
    var q = SessionInstance.QueryOver<Person>();
    q = q.Where(x => (x.PersonEnumType & type) == type);
    return q.List<Person>();
}

and PersonEnumType is a Enum flags :

[Flags]
public enum PersonEnumType
{
     Employee1 = 1,
     Employee2 = 2,
     Employee3 = 4
}

This throws Could not determine member from (Convert(x.PersonEnumType) & Convert(value(NHibernate.Repository.PersonRepositoryNh+<>c__DisplayClass2).type))

Of course this works in Nhibernate.Linq.

Why?

My guess is that with Linq the operation is done in memory so it will first load all the persons and then do the x.PersonEnumType & type filtering in memory. Or maybe the linq provider is just that good. Anyway [you can do it using ICriteria](http://stackoverflow.com/questions/1835392/hql-to-criteriaquery-when-using-bitwise-operators) — Toni Parviainen, Feb 21 '12 at 16:42

LeftyX · Answer 1 · 2012-02-21T18:04:10.297

if you've mapped your property properly in your mapping file:

<property name="PersonEnumType" type="MyApp.PersonEnumType, MyApp">
    <column name="Person" default="1" />
</property>

You can achieve what you're looking for using filters.
I don't know if this is the only solution but, here it goes:

You can create a filter definition:

<filter-def name="PersonEnumTypeFilter">
    <filter-param name="personType" type="MyApp.PersonEnumType, MyApp"/>
</filter-def>

and implement it in your class mapping:

<filter name="PersonEnumTypeFilter" condition="(:personType &amp; PersonEnumType) = PersonEnumType"/>

Now you can switch on your filter:

public IList<Person> SearchTest(PersonEnumType type)
{
    SessionInstance.EnableFilter("PersonEnumTypeFilter").SetParameter("personType",   type);
    var q = SessionInstance.Query<Person>();
    return q.ToList<Person>();
}

You can read more about filters here.

Only problem is that he doesn't want to use == but instead & — Toni Parviainen, Feb 21 '12 at 16:34

Nhibernate QueryOver by Enum Flags

1 Answers1