// eto naman kapag nag error ano gagawin
            d.OnErrorOccured += (object sender, OnErrorEventArg e) => {
                UIAlertView alrt = new UIAlertView("Error","An error has occured, what do you want to do?",null,"Kill yourself","Go home");
                alrt.Show();
            };
            // Perform any additional setup after loading the view, typically from a nib.
            btn.TouchUpInside += async (object sender, EventArgs e) => {
                //eto yung code ng pag tawag sa domain.
                Task<int> task = d.Add(1,1);
                int answer = await task;
                txt.Text = answer.ToString ();
            };