public void Action()
 {
     var request = new Request();
     var task = request.OperationAsync()
                       .ContinueWith(t => Callback(t, request));
 }
 public void Action2()
 {
     var request = new Request();
     var task = request.OperationAsync();
     Callback2(task, request);
 }
 public async Task Action()
 {
     var request = new Request();
     var task = request.OperationAsync();
     await Callback(task, request);
 }