How can you generically map a DbDataReader to a Castle.Windsor resolved type? - inversion-of-control

Question

This is confusing me, so this question will probably be confusing.
I have a an application that uses implementations of an IJob interface to accomplish different tasks.
public interface IJob
{
int Id { get; set; }
string Name { get; set; }
void Run();
}
I am using the Castle.Windsor.WindsorContainer to resolve these implementations, and using the service id to help identify them.
WindsorContainer container = new WindsorContainer(new XmlInterpreter());
IJob jobToExecute = container.Resolve<IJob>("nameOfJob");
I wrote a little generic extension method that simply puts the values of SQL columns into their corresponding properties.
public static void MapTo<T>(this DbDataReader reader, ref T instance) where T : class
{
Type objectType = typeof(T);
foreach (PropertyInfo propertyInfo in objectType.GetProperties())
{
if (propertyInfo.CanWrite)
{
int ordinal = -1;
try
{
ordinal = reader.GetOrdinal(propertyInfo.Name);
object value = reader[ordinal] == DBNull.Value ? null : reader[ordinal];
propertyInfo.SetValue(instance, value, null);
}
catch (IndexOutOfRangeException ex)
{
continue;
}
}
}
}
Now, because you can't instantiate an instance of an interface, passing an IJob to this method won't work. However, in order to gain the benefits of the IoC container, I need to do everything in my repository using the IJob interface. So, I wrote with this to resolve the IJob implementation, and pass it to the MapTo method to populate the necessary properties:
public IJob GetJobById(int id)
{
string cmdTxt = "SELECT Id, Name, Description, DateStarted, ScheduledCompletion, Completed FROM Jobs WHERE Id = #id";
using (DbCommand cmd = _dataFactory.CreateCommand(cmdTxt))
{
_dataFactory.AddParam(cmd, "id", id, DbType.Int32);
using (DbDataReader rdr = cmd.ExecuteReader())
{
if (rdr.Read())
{
IJob job = _container.Resolve<IJob>("job.implementation");
rdr.MapTo<IJob>(ref job);
return job;
}
else
{
return null;
}
}
}
}
Is this an OK design decision? Do you see any problems?

Answer 1

Well, for one, calling methods via reflection is usually not nice... and it looks like you're using Windsor as a type dictionary, which it is not...
I would write a non-generic MapTo (which would take a Type as parameter) that operates on an already-existing instance (when you create a new instance with Activator.CreateInstance you discard the instance Windsor had resolved) and then use it from the ComponentCreatedEvent event in IKernel. Something like this:
container.Kernel.ComponentCreated += (model, instance) => {
if (model.Service == typeof(IJob)) {
// select id,name from jobs where id = model.Name
// use MapTo to fill id,name into instance
}
}