T4mvc: Can't inherit a controller class that doesn't have a default constructor?

Question

I am using T4MVC with MVC2.

I have the following building blocks:

• A simple object interface that defines that each POCO object must have a long Id property:

   public interface IEntity { public long Id; } 

• A simple POCO class that implements the IEntity interface and has some string properties:

   public class CD : IEntity { public long Id { get; set; } public long Name { get; set; } } 

• Base controller:

   public abstract class EntityController<T> : Controller where T : class, global::IEntity { public EntityController(IEntityManager<T> manager); } 

• I use this base controller in my CDController (where CDManager implements the IEntityManager interface, which is the UnitOfWork template for adding CRUD functionality):

   public partial class CDController : EntityController<CD> { public CDController() : base(new CDManager()) { } } 

When I run my t4 template, this code is generated:

 namespace MyApp.Web.Controllers { public partial class CDController { [GeneratedCode("T4MVC", "2.0"), DebuggerNonUserCode] protected CDController(Dummy d) { } 

But this gives me an error at compile time:

MyApp.EntityController <CD-> does not contain a constructor that takes 0 arguments

How can i solve this?

Answer 1

I wanted the controller base class to be abstract, and the constructor to be protected and parameterized. Get this problem by adding an empty constructor to the ControllerBase that throws a NotImplementedException.

Not quite right, but he is doing his job. The only problem is that, in conjunction with dependency injection, the wrong constructor will be called - since it throws an exception, the application will crash.

the code:

 public abstract class ControllerBase : Controller { protected object AlwaysSupply { get; private set; } public ControllerBase() { throw new NotImplementedException(); } public ControllerBase(object alwaysSupply) { AlwaysSupply = alwaysSupply; } } 

This will cause T4MVC to create compiled code. It seems that the error is always trying to generate an empty constructor (without parameters) for controller classes.

Hope this helps someone.

Answer 2

I see the problem, and it boils down to the fact that T4MVC is not entirely correct when dealing with generic classes. Usually it generates a default ctor for it in a partial class, but the fact that it generates it discards.

You should be able to work simply by adding the default ctor yourself, for example.

 public abstract partial class EntityController<T> : Controller where T : class, IEntity { public EntityController() { } // etc... } 

Answer 3

I noticed something very strange:

I added an empty constructor to the base class, but without throw new NotImplementedException(); and it works great.

But here's the weird thing when you call the controller, if I have the url / {controller}? params (the default value is set to Index in RouteConfig) the taskless closed controller is called in the base class. But when do I have a url like / {controller} / {action}? Params, the constructor with parameters is called.