NHibernate linq query with IUserType

Question

In my project I use a IUserType (BooleanM1) that handles boolean values and writes -1 for true and 0 for false values to the database. So far everything works well. The mapping looks like this:

<property name="Active" column="ACTIVE" type="Core.Persistence.NH.Types.BooleanM1,Core.Test"/>

So if I do a query like the following

var pList = Session.Query<Test>().Where( c => c.Active ).ToList();

an exception is thrown:

NHibernate.QueryException: Unable to render boolean literal value [.Where[Core.Test.Domain.Test]
(NHibernate.Linq.NhQueryable`1[Core.Test.Domain.Test], Quote((c, ) => (c.Active)), )] 
---> System.InvalidCastException: Das Objekt des Typs "NHibernate.Type.CustomType" kann nicht 
in Typ "NHibernate.Type.BooleanType" umgewandelt werden.

The BooleanM1 implementation is like this:

{
  public class BooleanM1 :  IUserType
  {
     public bool IsMutable
     {
       get { return false; }
     }

     public Type ReturnedType
     {
        get { return typeof(bool); }
     }

     public SqlType[] SqlTypes
     {
        get { return new[]{NHibernateUtil.Int16.SqlType}; }
     }

     public object NullSafeGet(IDataReader rs, string[] names, object owner)
     {
        var obj = NHibernateUtil.String.NullSafeGet(rs, names[0]);

        if(obj == null ) return false;

        return ((string)obj == "-1" || (string)obj == "1") ? true : false;
     }

     public void NullSafeSet(IDbCommand cmd, object value, int index)
     {
        if(value == null)
        {
          ((IDataParameter) cmd.Parameters[index]).Value = DBNull.Value;
        }
        else
        {
          ((IDataParameter) cmd.Parameters[index]).Value = (bool)value ? -1 : 0;
        }
     }

     public object DeepCopy(object value)
     {
        return value;
     }

     public object Replace(object original, object target, object owner)
     {
        return original;
     }

     public object Assemble(object cached, object owner)
     {
       return cached;
     }

     public object Disassemble(object value)
     {
        return value;
     }

     public new bool Equals(object x, object y)
     {
       if( ReferenceEquals(x,y) ) return true;

       if( x == null || y == null ) return false;

       return x.Equals(y);
     }

     public int GetHashCode(object x)
     {
        return x == null ? typeof(bool).GetHashCode() + 473 : x.GetHashCode();
     }
}

Is this an known bug in the linq provider or is there something wrong with my UserType? Any help is appreciated.

Answer 1

I had a similar issue with a UserType that does pretty much the same thing. I found that explicitely stating the equality in my queries resolved the problem.

Try going from:

var pList = Session.Query<Test>().Where( c => c.Active ).ToList();

to:

var pList = Session.Query<Test>().Where( c => c.Active == true ).ToList();

For some reason NHibernate's Linq provider is then able to figure it out.

Answer 2

Fixed in version 4.1.0. The user type should implement IEnhancedUserType to work correctly with the fix. https://nhibernate.jira.com/browse/NH-2839

Answer 3

Have you solved this yet?

Not sure if it is the same issue but I had something similar where the database field was nullable and the custom type specifies that you are returning a "bool" -> It may need to be changed to "bool? for the return type"

 public Type ReturnedType
 {
    get { return typeof(bool?); }
 }