Error sending json in POST to web API service

another tip...where to add "content-type: application/json"...to the textbox field on the Composer/Parsed tab. There are 3 lines already filled in there, so I added this Content-type as the 4th line. That made the Post work.

In the HTTP request you need to set Content-Type to: Content-Type: application/json

So if you're using fiddler client add Content-Type: application/json to the request header

1. You have to must add header property Content-Type:application/json

2. When you define any POST request method input parameter that should be annotated as [FromBody], e.g.:

   [HttpPost]
   public HttpResponseMessage Post([FromBody]ActivityResult ar)
   {
     return new HttpResponseMessage(HttpStatusCode.OK);
   }
   

3. Any JSON input data must be raw data.