Entity Change Listener

Sometimes you want your application to react when an entity changes, e.g. to update a cache. Confinity offers the IEntityChangeListener interface for this purpose.

Prerequisites

The entity must inherit from ConfinityEntity.


public class Foobar : ConfinityEntity
{
    public string Name { get; set; } = null!;
}

Implementation

Inherit from IEntityChangeListener and implement the Handle method.


public class FoobarChangeListenerSimple(IFoobarCacheService foobarCacheService) : IEntityChangeListener
{
    public async Task Handle(IEnumerable<IEntityChange> changes)
    {
        await foobarCacheService.RebuildAsync();
    }
}

The Handle method gets invoked with a bunch of IEntityChange instances. You might want to evaluate them as followed.


public class FoobarChangeListenerComplex(IFoobarCacheService foobarCacheService) : IEntityChangeListener
{
    public async Task Handle(IEnumerable<IEntityChange> changes)
    {
        var changesList = changes.ToList();
        var idsToInvalidate = changesList
            .Where(p => p.IsDeletion)
            .Select(p => p.EntityId);
        await foobarCacheService.InvalidateAsync(idsToInvalidate);

        var idsToCache = changesList
            .Where(p => !p.IsDeletion)
            .Select(p => p.EntityId);
        await foobarCacheService.RebuildAsync(idsToCache);
    }
}

Registration

Register the implementation in your module configuration together with one or more entity types you want to monitor.


public void AddModule(IModuleContext module)
{
    module.Configure.RegisterChangeListener<FoobarChangeListenerSimple>(typeof(Foobar));
}

Notes

  • Listeners are executed in parallel
  • On the author instance listeners are triggered by the DbContext
  • On public instances listeners are triggered by the replication