Inject service into Action Filter

Question

I am trying to inject a service into my action filter but I am not getting the required service injected in the constructor. Here is what I have:

public class EnsureUserLoggedIn : ActionFilterAttribute {     private readonly ISessionService _sessionService;      public EnsureUserLoggedIn()     {         // I was unable able to remove the default ctor          // because of compilation error while using the          // attribute in my controller     }      public EnsureUserLoggedIn(ISessionService sessionService)     {         _sessionService = sessionService;     }      public override void OnActionExecuting(ActionExecutingContext context)     {         // Problem: _sessionService is null here         if (_sessionService.LoggedInUser == null)         {             context.HttpContext.Response.StatusCode = (int)HttpStatusCode.Unauthorized;             context.Result = new JsonResult("Unauthorized");         }     } } 

And I am decorating my controller like so:

[Route("api/issues"), EnsureUserLoggedIn] public class IssueController : Controller { } 

Startup.cs

services.AddScoped<ISessionService, SessionService>(); 

Answer 1

Using these articles as reference:

ASP.NET Core Action Filters

Action filters, service filters and type filters in ASP.NET 5 and MVC 6

Using the filter as a ServiceFilter

Because the filter will be used as a ServiceType, it needs to be registered with the framework IoC. If the action filters were used directly, this would not be required.

Startup.cs

public void ConfigureServices(IServiceCollection services) {     services.AddMvc();      services.AddScoped<ISessionService, SessionService>();     services.AddScoped<EnsureUserLoggedIn>();      ... } 

Custom filters are added to the MVC controller method and the controller class using the ServiceFilter attribute like so:

[ServiceFilter(typeof(EnsureUserLoggedIn))] [Route("api/issues")] public class IssueController : Controller {     // GET: api/issues     [HttpGet]     [ServiceFilter(typeof(EnsureUserLoggedIn))]     public IEnumerable<string> Get(){...} } 

There were other examples of

• Using the filter as a global filter

• Using the filter with base controllers

• Using the filter with an order

Take a look, give them a try and see if that resolves your issue.

Hope this helps.

Answer 2

Global filters

You need to implement IFilterFactory:

public class AuthorizationFilterFactory : IFilterFactory {     public bool IsReusable => false;      public IFilterMetadata CreateInstance(IServiceProvider serviceProvider)     {         // manually find and inject necessary dependencies.         var context = (IMyContext)serviceProvider.GetService(typeof(IMyContext));         return new AuthorizationFilter(context);     } } 

In Startup class instead of registering an actual filter you register your filter factory:

services.AddMvc(options => {     options.Filters.Add(new AuthorizationFilterFactory()); });