title: Some questions about webapi ActionFilterAttribtes, FilterProvider, and Dependency Injection
body: <p>I see that by default, an MVC4 WebApi project has 2 <code>IFilterProviders</code>: The <code>ConfigurationFilterProvider</code>, and the <code>ActionDescriptorFilterProvider</code>. When setting up a custom <code>IFilterProvider</code> to do property depenency injection, is it appropriate to remove both of these from the Filters collection first? Or is it more appropriate to just remove the <code>ActionDescriptorFilterProvider</code>, and leave the <code>ConfigurationFilterProvider</code> in the collection?</p>
  
  <p>Secondly, I see that after a WebApi Http <code>ActionFilterAttribute</code> is constructed for a particular action, it seems to stay around. For example when I put a custom action filter on an ApiController Get method, it is only constructed the first time that method is called. Subsequent calls to the api method seem to reuse the same filter (constructor breakpoints are only hit during the first invocation). Is this right? Why is it different than an MVC actionfilter, where a new instance is created for each method invocation?</p>