title: Calling Async Methods in Action Filters in MVC 5
body: <p>I'm writing an Action Filter (inheriting from <code>ActionFilterAttribute</code>) which uses <code>HttpClient</code> to POST data to an external server in the <code>OnResultExecuted</code> method. <code>HttpClient</code> has the method <code>PostAsync</code> which returns an awaitable <code>Task&lt;HttpResponseMessage&gt;</code>. </p>
  
  <pre><code>public override void OnResultExecuted(ResultExecutedContext filterContext)
  {
      using (var client = new HttpClient())
      {
          var task = client.PostAsync(GetUri(), GetContent());
          var result = task.Result; // blocking
      }
  }
  </code></pre>
  
  <p>The accepted answer to <a href="https://stackoverflow.com/questions/12482338/async-action-filter-in-mvc-4">Async action filter in MVC 4</a> says it is not possible in MVC 4. </p>
  
  <p>Is this still true in MVC 5, and if so what is the best way of calling this asynchronous method without blocking the thread?</p>