C# generics is keyword covariance / contravariance type inferral -

C# generics is keyword covariance / contravariance type inferral -

please consider interface:

public interface iinitialiazableentity<trepository> trepository : class, irepository { void initialize(trepository repository); }

this class (snippet):

public class somefacade<trepository> trepository : class, irepository { public void add<tentity>(tentity entity) tentity : abstractentity { seek { if (entity iinitialiazableentity<trepository>) (entity iinitialiazableentity<trepository>).initialize(this.repository); } grab (exception ex) { this.logger.error(ex); } } }

and entity:

public class pupil : abstractentity, iinitialiazableentity<irepository> { void initialize(irepository repository) { ... } }

since pupil iinitialiazableentity<irepository> , facade have actual repository more specialized basic irepository (i.e. imyspecialrepository : irepository), is keyword realize can cast imyspecialrepository , pass initialize method of entity? or if not, how it?

currently, if had instance somefacade<imyspecialrepository> code not work.

you have 2 options, 1 reply provided dan bryant, other create iinitialiazableentity<trepository> contravariant.

your interface declaration become (note in on generic type):

public interface iinitialiazableentity<in trepository> trepository : class, irepository { void initialize(trepository repository); }

this allow is check , cast work, iinitialiazableentity<irepository> can cast iinitialiazableentity<imyspecialrepository> when using contravariant generic.

see here more info covariance , contravariance in generics.

c# generics covariance contravariance