No 'MediaTypeFormatter' is available to read an object of type 'String'

Question

I'm using the ASP.NET Web API. I have an action in my controller which works fine if there's no parameter. If there is a parameter, like:

public string UploadFile(string actionType)

then my action isn't called and I get the following message, viewed in Fiddler:

No 'MediaTypeFormatter' is available to read an object of type 'String' with the media type 'multipart/form-data'

The route in my global.asx is as follows:

"api/{controller}/{action}/{actionType}"

I'm using Jquery Post to call the action:

    function upload() {

        var actiontype = $("input:radio[name=actiontype]").val();
        var formData = new FormData($('form')[0]); 

        $.ajax({
            url: 'api/uploads/uploadfile/' + actiontype,
            type: 'POST',
            success: function (data) {
                $("#mydiv").append(data);
            },
            error: function (data) {
                $("#mydiv").append(data);
            },
            data: formData,
            cache: false,
            contentType: false, 
            processData: false
        });
    };

Here's my action method:

    public string UploadFile(string actionType)
    {
        if (Request.Content.IsMimeMultipartContent())
        {
            //Save file
            MultipartFormDataStreamProvider provider = new MultipartFormDataStreamProvider(HttpContext.Current.Server.MapPath("~/Files"));
            Request.Content.ReadAsMultipartAsync(provider);
        }

        return string.Format("Action {0} Complete!", actionType);
    }

Is this a known problem, with a workaround? How can I have a simple action with parameter?

score 1 · Accepted Answer · edited May 23 '17 at 12:04

1

Assuming you're using the default routes, it looks like you're posting to an incorrect path. This is a common confusion that MVC developers seem to encounter (i know i did). MVC uses a default path like: /Controller/Action.

In web API's default routing setup, however, the action name is skipped (/api/Controller) then the method is found through the intersection of the HTTP verb name (post), the method name (Post___) and parameter if necessary.

Assuming you have an API controller named Uploads, you should have an action named PostUploadFile.

   $.ajax({
        url: 'api/uploads/',
        type: 'POST',

Some things to notice...

I started the name of your action with the text "Post..." this matters, the remainder of the name does not
Your post url was shorted to the name of the controller.
I went more in depth explaining the mapping here.

EDIT

Apparently your experiencing an odity of WebAPI. The way around this is to stuff your "actionType" parameter into a simple object, so model binding can take over.

Rick Strahl explains this and some other binding oddities here. There is also another SO question addressing similar issues.

edited May 23 '17 at 12:04

Community

1
1

answered May 07 '12 at 03:57

EBarr

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Thanks. Actually I'm using Web Forms - I have the Route Template defined as "api/{controller}/{action}/{actionType}" in the global file - it does expect the action. Remember, it works fine without the parameter there so I suspect it's got s/t to do with that. – Rivka May 07 '12 at 17:37
Webforms..huh? Does your controller inherit from `ApiController` ? Using firebug/fiddler/whatever ... what is listed in the request header `Accept`? Assuming you're excpecting json back it should be `application/json`. You may need `dataType: json` as part of your ajax call. – EBarr May 07 '12 at 18:27
My controller does inherite from apicontroller. In fiddler, the content-type is 'application/json'. I edited my OP to reflect my current ajax call. – Rivka May 07 '12 at 18:58
Thank you! That first link you posted to Rick's blog helped me. I used querystring/ParseQueryString() method (with no action parameter) which seemed to work. Appreciate your help. – Rivka May 07 '12 at 22:40

No 'MediaTypeFormatter' is available to read an object of type 'String'

1 Answers1