Service filters in ASP.NET MVC 6

Ontop of the already available action filters MVC 6 introduces Service filters. The newly introduced Service filters allow you to resolve a filter instance directly from the IoC container.

As the filters are registered in the container they can have a lifetime you control (i.e. singleton or transient) and can also use constructor injection.

The ability to control the lifetime of a filter is something annoyingly missing from previous versions of MVC where you couldn’t have a transient or a per-request filter created. This resulted in a lot of services created manually within the OnActionExecuting or OnActionExecuted methods.

A filter can now use constructor injection as below.

public interface ILogFilter { }

public class LogFilter : ActionFilterAttribute, ILogFilter
{
    private readonly ILog logger;

    public LogFilter(ILog logger)
    {
        this.logger = logger;
    }

    public override void OnActionExecuting(ActionExecutingContext actionContext)
    {
        this.logger.Warning("Log a message...");
    }
}

As long as the LogFilter is registered in the IoC container

public void ConfigureServices(IServiceCollection services)
{
    services.AddTransient<ILog, CustomLog>();
    services.AddSingleton<ILogFilter, LogFilter>();
}

It can be included on an action using the ServiceFilter filter factory attribute.

[ServiceFilter(typeof(ILogFilter))]
public IActionResult Index()
{
    return View();
}

Service filters in ASP.NET MVC 6