Web api return values for async methods

Question

I'm a bit confused with HttpResponseMessage and Task<HttpResponseMessage>.

If I'm using the HttpClient method PostAsync() to post data I need to give the Web Service method the Task<HttpResponseMessage> instead of HttpResponseMessage as return value as far as I understood things.

If I use Request.CreateResponse(HttpStatusCode.Forbidden, myError.ToString()); then I'm only getting the Response message object but not the Task object.

So my question here is how do I have to create the Fitting return for async calls to web api methods? (thus are my understandings there correct and if so how to best transform the message object int a Task<HttpResponseMessage> object)

The original code:

public HttpResponseMessage DeviceLogin(MyDevice device)
{
    EnummyError myError = EnummyError.None;

    // Authenticate Device.
    myError = this.Authenticate(device);

    if (myError != EnummyError.None)
    {
        return Request.CreateResponse(HttpStatusCode.Forbidden, myError.ToString());
    }
}

The updated Method header:

public Task<HttpResponseMessage> DeviceLogin(MyDevice device)

Answer 1

Web Api 2 has these abstraction classes which are now recommended to use. You can still use HttpResponseMessage (easier to follow for beginners, in my opinion), but Web Api 2 recommends using IHttpActionResult.

As for the return type, just did what you did before. Task<T> works automagically that way.

You also might want to check if this.Authenticate() has an async variant.

public async Task<IHttpActionResult> DeviceLogin(MyDevice device)
{
    EnummyError myError = EnummyError.None;

    // Authenticate Device.
    myError = this.Authenticate(device);

    // Perhaps Authenticate has an async method like this.
    // myError = await this.AuthenticateAsync(device);


    if (myError != EnummyError.None)
    {
        return ResponseMessage(Request.CreateResponse(Request.CreateResponse(HttpStatusCode.Forbidden, myError.ToString()));
    }
}

The ResponseMessage() method creates a ResponseMessageResult under water. This class derives from IHttpActionResult and accepts a HttpResponseMessage as a parameter in the constructor (which is made by Request.CreateResponse()).