MVC has areas, which would work nicely for this. My thoughts behind this are that it's nice to package functionality as modules, and areas serve that purpose well in MVC apps. Of course, it would be nice to be able to host nested areas, as well.

There is no way to forecast the execution order of WebApi Action Filters. It changes randomly each time the code is changed. It would be nice to have an integer property to control the order like in normal Mvc controllers, but also respecting the order they are put on the action method would be acceptable

In ASP.NET MVC it easy to cache the output of a call by applying the outputcache attribute. A similar feature for WebAPI would help for cacheable resources.

Support Depedency Injection for MessageHandlers by resolving the message handlers out of the ServiceResolver or providing a MessageHandlerFactory similar to the old WebApiConfiguration.MessageHandlerFactory.

The section on learning Web API needs to have a topic around writing unit tests. Web API home pages says it's 'easy to test' but then there are no topics around it. Please add a topic on unit testing

Right now it's impossible to add documentation of the multipart form data parameters and exclude / rename Model Binder arguments.

While I was working on WebAPIContrib I found several issues with the Routing API. I described it in more detail here: http://pedroreys.com/2012/03/14/asp-net-web-api-routing-needs-a-hug/

Support in Asp.Net Web Api OData for Groupping Agregates Rollup...

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&cad=rja&ved=0CGkQFjAG&url=https%3A%2F%2Fwww.oasis-open.org%2Fcommittees%2Fdownload.php%2F47409%2FOData-TC%2520F2F%25202012-11-09%2520Data%2520Aggregation.pptx&ei=v5XdUd3LG4a4qQG5iYCoBA&usg=AFQjCNEOIzDzLttGYUu2QfJ6dQOMuqJ7wA&sig2=_PqQz0dX-UnvhJsalRBtGw

http://cwebbbi.wordpress.com/2012/06/12/odata-extensions-for-data-aggregation/

https://www.oasis-open.org/committees/download.php/46084/ODataExtensionforDataAggregationv1.0.pdf

Currently the XML serialisers both output namespaces that are not required:

xmlns:xsd="http://www.w3.org/2001/XMLSchema"; xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";

I'm not sure about the Data Contract serializer, but it is not difficult to supress these...

Just pass into the Serialize method an XmlSerializerNamespaces:

var xmlSerializerNamespaces = new XmlSerializerNamespaces();
xmlSerializerNamespaces.Add(String.Empty, defaultNamespace);

var xmlSerializer = new XmlSerializer(objectType);
xmlSerializer.Serialize(xmlWriter, toBeSerialised, xmlSerializerNamespaces);

Where defaultNamespace could be set on the GlobalConfiguration.Configuration.Formatters.XmlFormatter or it could be read from the XmlRoot attribute (if present) on the object being serialised.

I think maintaining and working with ASP.NET MVC and ASP.NET Web API side by side in the same project is a drain on development resources and support cost.
I would like to use ASP.NET Web API to generate Razor views via an additional NuGet package rather then relying on ASP.NET MVC.

http://aspnetwebstack.codeplex.com/workitem/386

I think most people expectations would rightfully (IMHO) that WebAPI would support everything MVC does minus any view rendering or ActionResult overhead. When I search the web I see many comments relating to "I can do X in MVC but not in WebAPI". Example: Multipart/form-data or jsonp handling works in MVC out of the box.

Add an optional parameter to the HttpMethodAttributes to enforce SSL on methods/actions eg.

[HttpGet(SSL=Required)]
public .... Get(){}

[HttpPost(SSL=Optional)]
...

[HttpPut(SSL=NotSupported)]
...

The current Web Api Client is not compatible with Mono For Android, and trying to use HttpWebRequest and OData from Android mobile app. is a pain. Not sure about the amount of effort involved, but the author of Json.Net recently provided an mfa-compatible version, packaged as a Portable Class Library.

The System.Web.Mvc.HttpPostedFileBaseModelBinder class works well.

Can it be mirrored for the Web API