web api XmlMediaTypeFormatter exception
===

I want to use IoC / the dependency resolver of the web api framework for decoupling.

The XmlFormatter cant serialize interfaces,... Ok. But what would be the purpose of IoC and the DependencyResolver if I cant return xml?

I cant even do this:
(Method in my ApiController)

    public HttpResponseMessage Get()
            {
                IEnumerable<Project> projects = new List<IProject>() { new Project(), new Project() }.Select(p => p as Project);
    
                HttpResponseMessage response = Request.CreateResponse<IEnumerable<Project>>(HttpStatusCode.OK, projects);
    
                return response;
            }

I create a list of IProjects and cast them to 'Project'. But while creating the response I get this:

> The configured formatter
> 'System.Web.Http.Tracing.Tracers.XmlMediaTypeFormatterTracer' cannot
> write an object of type 'WhereSelectListIterator`2'.

That is a XmlMediaTypeFormatterTracer? I dont want tracing that throws errors while serialization. (BTW: I replaced the standard XMLformatter with my own one. However "XmlMediaTypeFormatterTracer" throws the exception...
Info: I get the same error while using the standard formatter)

Why is this XmlMediaTypeFormatterTracer called even if I implement my own xmlformatter?