c# - using a Handler in Web API and having Unity resolve per request

Question

I am using Unity as my IoC framework and I am creating a type based on the value in the header of each request in a handler:

var container = new UnityContainer();

container.RegisterType<IFoo,Foo>(new InjectionConstructor(valuefromHeader));

GlobalConfiguration.Configuration.DependencyResolver = 
    new Unity.WebApi.UnityDependencyResolver(container);

The problem is that the handler's SendAsync means that the global container is getting overwritten by different requests and the controllers that use IFoo in their constructor are getting the wrong values.

1) Can I make the SendAsync sync? 2) If not, how do I create different instances for each request and have the IoC container resolve safely?

I have looked at the following articles without success:

http://www.asp.net/web-api/overview/extensibility/using-the-web-api-dependency-resolver http://www.strathweb.com/2012/11/asp-net-web-api-and-dependencies-in-request-scope/ http://benfoster.io/blog/per-request-dependencies-in-aspnet-web-api-using-structuremap

Thanks in advance.

Answer 1

I agree with @Steven's approach, but that doesn't answer your more general question of how to resolve per request.

I would recommend you change to using the UnityHierarchicalDependencyResolver and then anything you register with HierarchicalLifetimeManager will be resolved per request.

Change this...

GlobalConfiguration.Configuration.DependencyResolver = 
    new Unity.WebApi.UnityDependencyResolver(container);

to this...

GlobalConfiguration.Configuration.DependencyResolver = 
    new Unity.WebApi.UnityHierarchicalDependencyResolver(container);