Hi all,

Ive just started using NHibernate so please forgive me if this issue has already been addressed (I did search but could find no answers)

I am using NHibernate v 1.2.0 and VS2005 sp1

I have a base abstract class that has a template

e.g
public abstract class BaseApplicationClass<Identifier>
{
public IList<Identifier> someStuff;
}

I inherit from this and supply the template in my subclasses

e,g
public class UpdateApplication : BaseApplicationClass<int>
public class ViewApplication: BaseApplicationClass<string>

so now the list someStuff in my UpdateApplication is an array of ints while the list someStuff in my ViewApplication is an array of strings

I am using a single table that has a row for each of the concrete classes (in this case different types of application)

e.g
ApplicationTable
(
ApplicationId int,
ApplicationName varchar(50)
)


so the rows in my DB would be

e.g
ApplicationId ApplicationName
--------------- -------------------
1 UpdateApplication
2 ViewApplication

I want to create a mapping file for the base class (I believe NHibernate wont try and instantiate abstract classes) and then use a subclass with a discriminator for each of the concrete class mapping files with each one extending my BaseApplicationClass based on the ApplicationName in the database



When I do this I get an error message saying that
"
NHibernate.MappingException:- Could not compile the mapping document 'BaseApplicationClass.hbm.xml'
NHibernate.MappingException:- persistent class BaseApplicationClass not found
System.TypeLoadException : Could not load type BaseApplicationClass

If I remove the template from the BaseApplicationClass it works a treat

I could skip using subclass and just have a class with a where statement for each subclass

e.g where="ApplicationName='UpdateApplication'"

but that feels a little "hacky"

Is this a known issue (or am I being a fool) and if so is there a fix ( I cant remove the template from my baseclass in the final solution BTW)

many thanks

W

After some digging around in the source Ive found what the problem is

Firstly MS mangles the class names for Templated classes

so for

public abstract class TemplatedClass<T1,T2>

the actual name of the type is TemplatedClass`2.

This is not a problem as I simply changed the name of the mapping file and the name attribute accordingly BUT it still failed

After further digging Ive found that a new DynamicMethod object is being created with the templated class as the owner....but unfortunately according to the MS documentation an ArgumentException is thrown if

"owner is an interface, an array, an open generic type, or a type parameter of a generic type or method."

So it looks like it is impossible in NHibernate to use a subclass of an abstract templated class (where the subclass supplies the template)

In my app I have a bunch of applications which contain an IList<UserType> - each application then specifies the type of user it can hold when deriving from the base abstract Application<UserType> class

anyone any suggestions ????

thanks

W

I added this line to the first line in the NHibernate.ReflectionOptimizer class

if (mappedType.IsGenericType && mappedType.IsAbstract) return;

which solved my problem