C# control events - Events in c# - c# - c# tutorial - c# net
- The Event is something special that is going to happen where Microsoft launches the events for the developer.
- Microsoft wants to aware the developer about the feature of the existing or new products, in this event.
- For this, Microsoft utilize Email or other advertisement options to aware the developer about the Event.
- At this case, Microsoft will work as a publisher who raises the Event and notifies the developers about it.
- Here, developers will work as the subscriber of the Event who handles the Event.
- At C#, Event can be publisher, subscriber, notification and a handler.
- Generally, the User Interface uses the events and here we will take an example of Button control in Windows.
- In C#, Button performs multiple events such as click, mouseover, etc.
- The custom class contains the Event through which we will notify the other subscriber class about the other things which is going to happen.
- In this case, we will define the Event and inform the other classes about the Event, which contains the event handler.
- In C# and .NET both support the events with the delegates and it is an encapsulated delegate.
- Events and delegates give the notification to the client application, when the state of the application changes.
- Events and delegates both are tightly coupled for dispatching the events, and event handling require the implementation of the delegates.
- The sending event class is known as the publisher, and the receiver class or handling the Event is known as a subscriber.
Key Points about the Events are
- At C#, event handler will take the two parameters as input and return the void.
- The first parameter of the Event is also known as the source, which will publish the object.
- The subscriber will determine what response we have to give, where the publisher will decide when we have to raise the Event.
- Generally, we used the Event for the single user action like clicking on the button.
c# Button Control Events… :
- OnClick – when user clicks a button
- OnCommand – When user clicks button
- OnLoad – When page first loads and button loads
- OnInit – When button is initialized
- OnPreReader- just before button is drawn
- OnUnload – When button is unloaded from memory
- OnDisposed – When button is released from memory
- OnDataBinding – When button is bound to a data source
Declaration of the event
Steps for implementing the Event
- Firstly, the event type of the delegate must be declared, for the declaration of the Event in the class.
Declaration of the Event
Invokation of the Event
Hooking up the Event
Detach the Event
- Delegates works as a pointer to a function and it is a reference data type and it holds the reference of the method. System.Delegate class implicitly derived all the delegates.