差分

var alert = UIAlertController.Create("title", "message", UIAlertControllerStyle.Alert);

alert.AddAction(UIAlertAction.Create("NO", UIAlertActionStyle.Cancel , (handler) => { Console.WriteLine("NO"); }));

alert.AddAction(UIAlertAction.Create("YES", UIAlertActionStyle.Default, (handler) => { Console.WriteLine("YES: " + alert.TextFields[0].Text); }));

alert.AddTextField((textfield) => { textfield.Placeholder = "textfield";

// var label = new UILabel(new CGRect(0, 0, 80, 30)); label.Text = "LABEL: ";

textfield.LeftView = label; textfield.LeftViewMode = UITextFieldViewMode.Always; });

this.PresentViewController(alert, animated: true, completionHandler: null);