ASP.NET Core MVC controllers in separate assembly

Question

I'm using ASP.NET MVC Core RC-2. I have a web project targeting the full .NET framework. I also have a separate class library in the solution, also targeting the full framework.

In the class library, I have a controller, marked with a route attribute. I have referenced the class library from the web project. This assembly references the nuget package Microsoft.AspNetCore.Mvc v. 1.0.0-rc2-final.

It was my understanding that this external controller would be discovered automatically, e.g. http://www.strathweb.com/2015/04/asp-net-mvc-6-discovers-controllers/

However this doesn't work for me- I browse to the URL of the route and I get a blank page and it doesn't hit my controller breakpoint.

Any ideas how to get this working?

Interestingly, it does seem to work for web projects targeting .NET Core Framework, referencing a class library also targeting .NET Core. But not for a web project targeting the full framework, referencing a standard .NET class library.

Note: this is MVC Core which is supposed to support this kind of scenario without any MVC<=4 routing overrides.

Possible duplicate of [How to register a Controller into ASP.NET MVC when the controller class is in a different assembly?](http://stackoverflow.com/questions/7560005/how-to-register-a-controller-into-asp-net-mvc-when-the-controller-class-is-in-a) — Oscar, Jun 09 '16 at 12:27

score 75 · Answer 1 · edited Oct 16 '18 at 15:50

75

Still an issue in ASP.Net Core 1.0, not sure if it's by design now. Easiest solution is to do this in Startup.cs/ConfigureServices

services.AddMvc()
  .AddApplicationPart(typeof(<class in external assembly>).Assembly)
  .AddControllersAsServices();

AddApplicationPart explicitly includes the assembly in searches for controllers. The call to AddControllersAsServices() will add all the discovered controllers into the services collection, and if you put a breakpoint after this line and inspect 'services', you will see in the collection all the controller types which have been found.

You might also want to check here: https://docs.asp.net/en/latest/migration/rc1-to-rtm.html#asp-net-5-mvc-compile-views as the discovery rules are now changed for controllers from RC1.

Also remember to use IActionResult instead of ActionResult!

edited Oct 16 '18 at 15:50

Peter Ruderman

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answered Jul 07 '16 at 18:17

James Ellis-Jones

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For me only using `.AddApplicationPart(typeof().Assembly)` was enough. You can also use another line instead: `.AddApplicationPart(Assembly.Load("ExternalAssemblyName"));` – Learner Aug 10 '16 at 10:46
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It must be by design now, it would be horrific to turn this on after the fact. – Ciantic Jan 31 '17 at 19:55
Done the same thing but not succeed – DanilGholtsman Aug 04 '17 at 13:38
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Any way to bring in a specific controller without bringing in all of them in the other assembly? – Brandon Cuff Sep 06 '18 at 22:57

score 7 · Accepted Answer · answered Jun 09 '16 at 20:24

I believe you are hitting the following known issue in RC2. https://github.com/aspnet/Mvc/issues/4674 (workaround is mentioned in the bug)

This has been fixed since then but will only be available in next release (unless you are ok with using nightly builds)

ASP.NET Core MVC controllers in separate assembly

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