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This article mainly introduces "the life cycle analysis of ASP.NET server controls". In the daily operation, I believe that many people have doubts about the life cycle analysis of ASP.NET server controls. The editor has consulted all kinds of materials and sorted out simple and easy-to-use operation methods. I hope it will be helpful to answer the doubts of "life cycle analysis of ASP.NET server controls". Next, please follow the editor to study!

The life cycle of ASP.NET server controls is the most important concept for creating server controls. As a developer, you must have a deep understanding of the life cycle of ASP.NET server controls. Of course, this cannot be done overnight. For beginners who learn the technology of control development, they do not need to master it in great detail, but only need to have a general understanding of the different stages of the life cycle of the server control.

In the process of mastering the life cycle of ASP.NET server controls, readers should pay special attention to the relevant content about the state of server controls. While focusing on the various stages of the life cycle, we should pay attention to the following questions about the state changes of the server control: when to save the control and restore its state during the life cycle of the control; when to interact with the page and other controls; when to execute important processing logic At each stage, what information the control can use, what data it holds, what state the control is in when it is rendered, and when to output display markup text, and so on. The 11 phases that the life cycle of the ASP.NET server control goes through are listed below.

(1) initialization: in this phase, two main tasks are completed: first, initializing the settings required during the life cycle of the incoming Web request; and second, tracking the view state. First, the page framework raises the Init event by default and calls the OnInit () method, which the control developer can override to provide initialization logic for the control. After that, the page framework calls the TrackViewState method to track the view state. It is important to note that in most cases, the TrackViewState method implementation provided by the Control base class is sufficient. Developers may need to override TrackViewState methods only if the control defines complex properties.

(2) load view state: the main task of this phase is to check whether the ASP.NET server control exists and whether its state needs to be restored to the state where it ended before the request was processed. Therefore, this process occurs during the page return process, rather than initializing the request process. At this stage, the page framework automatically restores the ViewState dictionary. If the server control does not maintain its state, or if it has the ability to save all its state by default and use the ViewState dictionary, then the developer does not have to implement any logic. For those data types that cannot be stored in the ViewState dictionary or where custom state management is required, developers can override the LoadViewState method to customize state recovery and management.

(3) handle postback data: if you want the control to check the form data sent back by the client, you must implement the LoadPostData () method of the System.Web.UI.IPostBackDataHandler interface. Therefore, only controls that handle postback data participate in this phase.

(4) loading: at this stage, the ASP.NET server control in the control tree has been created and initialized, the state has been restored, and the form control reflects the client's data. At this point, the developer can implement the common logic for each request by overriding the OnLoad () method.

(5) send postback change notification: at this stage, the ASP.NET server control signals the change in control state due to the postback by raising an event (so this phase is used only during the postback process). To establish this signal, the developer must use the System.Web.UI.IPostBackDataHandler interface again and implement another method-RaisePostBackChangedEvent (). The judgment process is that if the state of the control changes due to a postback, LoadPostData () returns true; otherwise it returns false. The page framework tracks all controls that return true and calls RaisePostDataChangedEvent () on those controls.

(6) handle postback events: this stage deals with client events that cause postback. To facilitate mapping client-side events to server-side events for processing, developers can implement this logic at this stage by implementing the RaisePostBackEvent () method of the System.Web.UI.IPostBackEventHandler interface. In this way, the server control will successfully capture the postback client event for server-side processing.

(7) pre-rendering: this phase completes any work required before the control is generated. This is usually done by overriding the OnPreRender () method. It is important to note that at this stage, changes made to the state of the control at the pre-rendering stage can be saved, while changes made during the rendering phase are lost.

(8) Save state: if the ASP.NET server control does not maintain state, or if it has the ability to save all its state by default and use the ViewState dictionary, then the developer does not have to implement any logic at this stage. Because the process of saving the state is automatic. If the ASP.NET server control requires custom state saving, or if the control cannot store special data types in the ViewState dictionary, you need to override the SaveViewState () method to achieve state saving.

(9) rendering: represents the process of writing tagged text to the HTTP output stream. The developer overrides the Render () method to customize the markup text on the output stream.

(10) disposal: in this phase, you release references to expensive resources, such as database links, by overriding the Dispose () method.

(11) uninstall: the work done is the same as the "disposal" phase, but developers typically perform cleanup in the Dispose () method instead of handling the Unload event.

At this point, the study on the life cycle analysis of ASP.NET server controls is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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