title: Set default Media Formatter for a WebAPI action
body: <p>I have implemented a custom media formatter and it works great when the client specifically requests "csv" format. </p>
  
  <p>I have tested my api controller with this code:</p>
  
  <pre><code>        HttpClient client = new HttpClient();
          // Add the Accept header
          client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("text/csv"));
  </code></pre>
  
  <p>However, when I open the same URL from a web browser it returns JSON not CSV. This is probably due to standard ASP.NET WebAPI configuration that sets JSON as the default media formatter unless otherwise specified by the caller. I want this default behavior on every other web service I have but NOT on this single operation that returns CSV. I want the default media handler to be the CSV handler that I implemented. How do I configure the Controller's endpoint such that it returns CSV by default and only returns JSON/XML if requested by the client?</p>