(429 words)

I like using NPoco, it’s a really nice library that allows you stop having to write raw ADO.NET. Recently I just switched one of my projects at work to use the Fluent Mapping features, essentially so that my POCO’s do not need to have the mapping attributes in them.

I started wth the example on the NPoco wiki of creating a database factory, and adding the mapping class to the fluent configuration. As the number of mapping classes has grown, this has quickly become unwieldy and a bit of a maintainance issue.

As I already utilise Structuremap in the application, I wanted to configure it to automatically pick up my mapping classes and build the configuration object for me. This is easy to in the registry:

public DefaultRegistry()
{
	Scan(
		scan =>
		{
			scan.TheCallingAssembly();
			scan.WithDefaultConventions();
			scan.With(new ControllerConvention());
			scan.AddAllTypesOf<IMap>();
		});

	For<FluentConfig>().Use(context => FluentMappingConfiguration.Configure(context.GetAllInstances<IMap>().ToArray()));
	For<DatabaseFactory>().Singleton().Use<DatabaseFactory>();
	For<IDatabase>().HttpContextScoped().Use(context => context.GetInstance<DatabaseFactory>().GetDatabase());
}

The mapping classes must inherit from Map<T>, which itself inherits from IMap. Thus we can confidently add all types of IMap in the scan.

Then an instance of FluentConfig must be registered, which can be done with an overload of .Use, from which we get the StructureMap context and pull out all the types of IMap which have been found and pass it to the static .Configure method of the FluentMappingConfiguration, which constructs the instance.

The DatabaseFactory (see below) is then registered, and it accepts a ‘FluentConfig’ instance in its constructor. As per the original example on the NPoco wiki, it is marked as a singleton to ensure that only one instance is created, so that the mappings do not get registered more than once. I don’t know what would happen if the mappings were to be registered more than once, but I assume that it would be a Bad Thing™.

Then, for the NPoco IDatabase instance that we register, we want to always create it using the instance of the DatabaseFactory that has already been registered, which again is accessible using the overload of .Use to get the Structuremap context. It’s marked as .HttpContextScoped(), but I’m honestly not sure if that’s required or not given that I’m using Structuremap.MVC5 nested containers.

For completeness, here is the DatabaseFactory:

public class DatabaseFactory
{
	private static NPoco.DatabaseFactory _internalFactory;

	public DatabaseFactory(FluentConfig fluentConfig)
	{
		Configure(fluentConfig);
	}

	private static void Configure(FluentConfig fluentConfiguration)
	{
		_internalFactory = NPoco.DatabaseFactory.Config(x =>
		{
			x.UsingDatabase(() => new Database("ConnectionString"));
			x.WithFluentConfig(fluentConfiguration);
		});
	}

	public NPoco.Database GetDatabase()
	{
		return _internalFactory.GetDatabase();
	}
}

Stuart Grassie

A software developer in the North of England.