Get Injected Object in ASP.NET vNext filter

Question

I'm trying to create my custom authorize attribute, but in asp.net vnext using the default dependency injection framework I don't how to get the injected object. I need to get the injected object in the default ctor.

   public  class CustomAttribute
{

   private IDb _db;

   public CustomAttribute()
   {
       _db = null; // get injected object
   }

   public CustomAttribute(IDb db)
   {
       _db = db;
   }

   // apply all authentication logic
}

Answer 1

You can use the ServiceFilterAttribute for this purpose. The service filter attribute lets the DI system take care of instantiating and maintaining the lifetime of the filter CustomAuthorizeFilter and its any required services.

Example:

// register with DI
services.AddScoped<ApplicationDbContext>();
services.AddTransient<CustomAuthorizeFilter>();

//------------------

public class CustomAuthorizeFilter : IAsyncAuthorizationFilter
{
    private readonly ApplicationDbContext _db;

    public CustomAuthorizeFilter(ApplicationDbContext db)
    {
        _db = db;
    }

    public Task OnAuthorizationAsync(AuthorizationContext context)
    {
        //do something here    
    }
}

//------------------

[ServiceFilter(typeof(CustomAuthorizeFilter))]
public class AdminController : Controller
{
    // do something here
}