Async

public Task<HttpResponseMessage> EventHandler(string confirmKey)
        {
            var eventModel = new EventResultModel(User.Identity.Name);
            return Task<HttpResponseMessage>.Factory.StartNew(() =>
                {
                    eventModel.PrepareModel(confirmKey);
                    return Request.CreateResponse(HttpStatusCode.OK, eventModel);
                });
        }

// OR

public async Task<HttpResponseMessage> EventHandler(string confirmKey)
        {
            var eventModel = new EventResultModel(User.Identity.Name);
            return await Task<HttpResponseMessage>.Factory.StartNew(() =>
                {
                    eventModel.PrepareModel(confirmKey);
                    return Request.CreateResponse(HttpStatusCode.OK, eventModel);
                });
        }