Model binding on POST

I have this simple controller:

public class TestController : ApiController
    {
         
        public HttpResponseMessage Get(string id)
        {
            return new HttpResponseMessage(HttpStatusCode.OK);
        }

        public HttpResponseMessage Post(string id)
        {
            var content = Request.Content.ReadAsStringAsync().Result;
            return new HttpResponseMessage(HttpStatusCode.OK);
        }

    }

The route is this:

routes.MapHttpRoute(
                "test",
                "{controller}/asdf/{id}"

Could you explain on this simple scenario why would this test pass:

var uri = new Uri(baseUri, "test/asdf/someId")
response = client.GetAsync(uri).Result;
response.EnsureSuccessStatusCode();

And this fail:

var uri = new Uri(baseUri, "test/asdf/someId")
response = client.PostAsync(uri, new StringContent("some content")).Result;
response.EnsureSuccessStatusCode();

The secod test fails with InvalidOperationException: 'Headers.ContentType' must be set before 'ObjectContent' can serialize its content. The controllers Post method isn't invoked. The test passes if the 'id' parameter of the Post action is removed.

Thanks

Re: Model binding on POST

The reason you are getting the InvalidOperationException on the Post is due to the fact that there is not a "text/plain" media type formatter in the framework. You will need to create a custom MediaTypeFormatter that understands this content-type. Also, make sure to add the new formatter to your HttpConfiguration formatters collection during application startup.

Cheers,

Dave

Re: Model binding on POST

I should elaborate on this response. WebAPI is trying to model bind your "someId" parameter, and looks for a plain/text formatter and pukes since there is not one available. If you remove your parameter (a parameterless Post method) then it works fine.

Re: Model binding on POST

Thanks for your replies. They were really helpful.

Instead of creating MediaTypeFormatter for 'text/plain' I'm now relying on built in formatter for application/xml by sending an object with content type set to 'application/xml'. Now it works fine but one thing. My {id} URL segment is bound to GET action as expected, but it's null on POST.

The controller:

public class TestController : ApiController
    {
        public HttpResponseMessage Get(string id)
        {
            return new HttpResponseMessage(HttpStatusCode.OK);
        }

        public HttpResponseMessage Post(string id, Content content)
        {
            return new HttpResponseMessage(HttpStatusCode.OK);
        }
    }

    public class Content
    {
        public string Value { get; set; }
    }

When GET request is sent with this code:

   var response = client.GetAsync("test/asdf/someId");

I can see in the debugger the value of 'id' argument in Get action being 'someId'.

When POST is sent:

var request = new HttpRequestMessage();
var content = request.CreateContent(new Content { Value = "some content" });
content.Headers.ContentType = MediaTypeHeaderValue.Parse("application/xml");

var response = client.PostAsync("test/asdf/someId", content).Result;

in the debugger in the Post action I see 'content' argument being model bound correctly and 'id' being null.

What's the move here to get 'id' bound to Post action as well?

Thanks,
Vitaly

Re: Model binding on POST

I actually have the exact same problem. With POST and body parameters, I can either get complex working or primitives working, but not both at the same time.

To get a complex parameter working, I need to change the Read Policy to AsSingleObject - but this breaks the other parameters that were correctly bound by model binding.

Re: Model binding on POST

This was confirmed as a bug which should be fixed in the next version.