title: The batch request must have a "Content-Type" header / "multipart/mixed" as the media type
body: <p>Got an error after I add the DefaultODataBatchHandler on my WEB API OData v4.</p>
  
  <pre><code>DefaultODataBatchHandler defaultODataBatchHandler = new DefaultODataBatchHandler(GlobalConfiguration.DefaultServer); 
  </code></pre>
  
  <p>In browser I've got this error: <strong>The batch request must have a "Content-Type" header.</strong>
  In POSTMan I've got this error: <strong>The batch request must have 'multipart/mixed' as the media type.</strong></p>
  
  <p>If I didn't put the code above. I've got this error when accessing the <strong>$batch</strong></p>
  
  <pre><code>"Message": "No HTTP resource was found that matches the request URI 'http://localhost:2288/$batch'.",
  "MessageDetail": "No route providing a controller name was found to match request URI 'http://localhost:2288/$batch'"
  </code></pre>
  
  <p>RouteConfig.cs</p>
  
  <pre><code>public class RouteConfig
  {
      public static void RegisterRoutes(RouteCollection routes)
      {
  
          routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
  
          routes.MapRoute(
              name: "Default",
              url: "{controller}/{action}/{id}",
              defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
          );
      }
  }
  </code></pre>