This is more of a blog post about what not to do :)

At first glance, it would seem relatively painless to change your WebApi controller’s configuration, I’d assume most people would do what I initially did. Say for example you wanted to have your controller only support JSON, here’s what I initially tried (DO NOT DO THIS):

protected override void Initialize(HttpControllerContext controllerContext)
{
    base.Initialize(controllerContext);
    var toRemove = controllerContext.Configuration.Formatters
        .Where(t => (t is JsonMediaTypeFormatter) == false).ToList();
    foreach (var r in toRemove)
    {
        controllerContext.Configuration.Formatters.Remove(r);
    }
}

Simple right, just override initialize in your controller and change the current controllerContext’s configuration…. WRONG :(

What this is actually doing is modifying the global WebApi configuration though it’s not clear that this is the case. Unfortunately the actual Configuration property on the controllerContext instance is assigned to the global one. I’m assuming the WebApi team has done this for a reason but I’m not sure what that is; as seen above it’s very easy to change the global WebApi configuration at runtime. Seems to me like it might have been a better idea to clone the global configuration instance and assign that to each HttpControllerContext object.

The correct way to specify per controller custom configuration in WebApi is to use the IControllerConfiguration interface. You can read all about here and it is fairly simple but it does seem like you have to jump through a few hoops for something that initially seems very straight forward.