How do I get StructureMap working with an AngularJs / MVC5 and WebApi2 web project

Question

So I have an AngularJs/MVC project with normal Controllers and decided to move more to an SPA app and add WebApi2 to pass data back to my UI instead of using MVC.

In my Global.asax I had the following for my MVC project:

DependencyResolver.SetResolver(new StructureMapDependencyResolver(container));

My WebApiController has a constructor with an IRepository to talk to the database and get some entities back. When my AngularJS web app makes a call to the controller the break points never hit and I'm getting server 500 errors returned with very little information.

Public class MyController : ApiController
{
    public MyController (IThingRepository thingrepository)
    {
    ....
    }
}

I started seeing errors like:

"ExceptionType": "System.ArgumentException", "Message": "Type 'MyProject.Web.Controllers.MyController' does not have a default constructor"

I don't want to add a default constructor. Why am I getting this and how do I fix it?

Answer 1

This is happening because dependency resolution isn't working for the WebApi controller. StructureMap isn't finding the constructor and can't resolve the IThingRepository.

WebApi and MVC work differently and have slightly different dependency resolution mechanics. The Global.asax code "DependencyResolver.SetResolver" works for MVC but not for WebAPi. So how do we get this working?

1. Install the nuget package StructureMap.MVC5 which has the plumbing to make this work.

   Install-Package StructureMap.MVC5

2. Create a new StructureMapDependencyResolver Class that works for both MVC and WebApi

   public class StructureMapDependencyResolver : StructureMapDependencyScope, IDependencyResolver
   {
       public StructureMapDependencyResolver(IContainer container) : base(container)
       {
       }
       public IDependencyScope BeginScope()
       {
            IContainer child = this.Container.GetNestedContainer();
            return new StructureMapDependencyResolver(child);
       }
   }
   

3. Update the Global.asax code:

   //StructureMap Container
   IContainer container = IoC.Initialize();
   
   //Register for MVC
   DependencyResolver.SetResolver(new StructureMapDependencyResolver(container));
   
   //Register for Web API
   GlobalConfiguration.Configuration.DependencyResolver = new StructureMapDependencyResolver(container);
   

For a full explanation of what is happening check this blog post on ASP.NET MVC 4, Web API and StructureMap