title: No 'MediaTypeFormatter' is available to read an object of type 'String'
body: <p>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:</p>
  
  <pre><code>public string UploadFile(string actionType)
  </code></pre>
  
  <p>then my action isn't called and I get the following message,  viewed in Fiddler:</p>
  
  <blockquote>
    <p>No 'MediaTypeFormatter' is available to read an object of type 'String' with the media type 'multipart/form-data'</p>
  </blockquote>
  
  <p>The route in my <code>global.asx</code> is as follows:</p>
  
  <pre><code>"api/{controller}/{action}/{actionType}"
  </code></pre>
  
  <p>I'm using Jquery Post to call the action:</p>
  
  <pre><code>    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
          });
      }; 
  </code></pre>
  
  <p>Here's my action method:</p>
  
  <pre><code>    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);
      }
  </code></pre>
  
  <p>Is this a known problem, with a workaround? How can I have a simple action with parameter?</p>