Question

Having successfully gotten a sample program working, I’m now starting
to do Real Work with Fluent NHibernate – trying to use Automapping on my project’s class
heirarchy.

It’s a scientific instrumentation application, and the classes I’m
mapping have several properties that are arrays of floats e.g.

    private float[] _rawY; 
    public virtual float[] RawY 
    { 
        get 
        { 
            return _rawY; 
        } 
        set 
        { 
            _rawY = value; 
        } 
    } 

These arrays can contain a maximum of 500 values.

I didn’t expect Automapping to work on arrays, but tried it anyway,
with some success at first. Each array was auto mapped to a BLOB
(using SQLite), which seemed like a viable solution.

The first problem came when I tried to call SaveOrUpdate on the
objects containing the arrays – I got “No persister for float[]”
exceptions.

So my next thought was to convert all my arrays into ILists e.g.

public virtual IList<float> RawY { get; set; } 

But now I get:

NHibernate.MappingException: Association references unmapped class: System.Single 

Since Automapping can deal with lists of complex objects, it never
occured to me it would not be able to map lists of basic types. But
after doing some Googling for a solution, this seems to be the case.
Some people seem to have solved the problem, but the sample code I
saw requires more knowledge of NHibernate than I have right now – I
didn’t understand it.

Questions:

1. How can I make this work with Automapping?

2. Also, is it better to use arrays or lists for this application?

I can modify my app to use either if necessary (though I prefer
lists).

Edit:

I’ve studied the code in Mapping Collection of Strings, and I see there is test code in the source that sets up an IList of strings, e.g.

public virtual IList<string> ListOfSimpleChildren { get; set; }

[Test] 
public void CanSetAsElement() 
{ 
    new MappingTester<OneToManyTarget>() 
        .ForMapping(m => m.HasMany(x => x.ListOfSimpleChildren).Element("columnName")) 
        .Element("class/bag/element").Exists(); 
} 

so this must be possible using pure Automapping, but I’ve had zero luck getting anything to work, probably because I don’t have the requisite knowlege of manually mapping with NHibernate.

Starting to think I’m going to have to hack this (by encoding the array of floats as a single string, or creating a class that contains a single float which I then aggregate into my lists), unless someone can tell me how to do it properly.

End Edit

Here’s my CreateSessionFactory method, if that helps formulate a
reply…

    private static ISessionFactory CreateSessionFactory() 
    { 
        ISessionFactory sessionFactory = null; 


        const string autoMapExportDir = "AutoMapExport"; 
        if( !Directory.Exists(autoMapExportDir) ) 
            Directory.CreateDirectory(autoMapExportDir); 


        try 
        { 
            var autoPersistenceModel = 
                AutoMap.AssemblyOf<DlsAppOverlordExportRunData>() 
                       .Where(t => t.Namespace == "DlsAppAutomapped") 
                       .Conventions.Add( DefaultCascade.All() ) 
                ; 


            sessionFactory = Fluently.Configure() 
                .Database(SQLiteConfiguration.Standard 
                              .UsingFile(DbFile) 
                              .ShowSql() 
                         ) 
                .Mappings(m => m.AutoMappings.Add(autoPersistenceModel) 
                                             .ExportTo(autoMapExportDir) 
                         ) 
                .ExposeConfiguration(BuildSchema) 
                .BuildSessionFactory() 
                ; 
        } 
        catch (Exception e) 
        { 
            Debug.WriteLine(e); 
        } 


        return sessionFactory; 
    } 

Answer 1

Since I posted my question, the Fluent NHibernate team have fixed this problem.

You can now automap ILists of C# value types (strings, ints, floats, etc).

Just make sure you have a recent version of FNH.

Edit

I recently upgraded from FNH 1.0 to FNH 1.3.

This version will also automap arrays – float[], int[], etc.

Seems to map them as BLOBs. I assume this will be more efficient than ILists, but have not done any profiling to confirm.