title: MVC 4 Global Exception Filter how to implement?
body: <p>How do I implement a global exception handler in  MVC4 as it seems to be different from MVC3.</p>
  
  <p>Not sure how to implement the following:</p>
  
  <pre><code>public class ErrorHandlerAttribute: System.Web.Mvc.FilterAttribute, 
                                      IExceptionFilter
  {
      public Task ExecuteExceptionFilterAsync(
              HttpActionExecutedContext actionExecutedContext, 
              CancellationToken cancellationToken)
      {
          throw new NotImplementedException();
      }
  }
  </code></pre>