The MonoTouch API supports two styles of event notification: the Objective-C style that uses a delegate class or the C# style using event notifications.

The C# style allows the user to add or remove event handlers at runtime by assigning to the events of properties of this class. Event handlers can be anyone of a method, an anonymous methods or a lambda expression. Using the C# style events or properties will override any manual settings to the Objective-C Delegate or WeakDelegate settings.

The Objective-C style requires the user to create a new class derived from UIKit.UITextFieldDelegate class and assign it to the UIKit.Delegate property. Alternatively, for low-level control, by creating a class derived from Foundation.NSObject which has every entry point properly decorated with an [Export] attribute. The instance of this object can then be assigned to the UITextField.WeakDelegate property.