barcode library c# Figure 2-10. What happens each time the client requests a page in Font

Creating Code 39 in Font Figure 2-10. What happens each time the client requests a page

Figure 2-10. What happens each time the client requests a page
USS Code 39 Creation In None
Using Barcode generation for Font Control to generate, create USS Code 39 image in Font applications.
www.OnBarcode.com
QR Code 2d Barcode Drawer In None
Using Barcode maker for Font Control to generate, create Quick Response Code image in Font applications.
www.OnBarcode.com
CHAPTER 2 WEB DEVELOPMENT IN .NET
Create EAN / UCC - 14 In None
Using Barcode maker for Font Control to generate, create USS-128 image in Font applications.
www.OnBarcode.com
Barcode Drawer In None
Using Barcode drawer for Font Control to generate, create Barcode image in Font applications.
www.OnBarcode.com
The System.Web.UI.Page class, from which every page ultimately inherits, exposes these stages for you to consume and customize. There s a common pattern for customizing these phases: you can attach a handler for an event, such as Init or Load, or you can override a corresponding method on the page class, such as OnInit or OnLoad. In Figure 2-10, there are five main stages Init, Load, Control Events, PreRender, and Unload and you are able to add code that is processed at each of them. Other actions also occur between these main phases, completing the picture of how a page is processed. As we said, the main events can be handled in two ways: by attaching to the event itself or by overriding the corresponding method. For example, there s an Init event and an OnInit virtual method you can override. When you override, you must always remember to call the base class method, as in the following example: Protected Overrides Sub OnPreRender(ByVal e As System.EventArgs) MyBase.OnPreRender(e) ' Do our stuff End Sub This ensures that all built-in processing implemented in the base class is properly executed. Most notably, calling the base method implementation ensures the appropriate event is fired. Let s analyze each of the five stages of a page s lifecycle.
Make Code 128 Code Set B In None
Using Barcode generator for Font Control to generate, create Code 128C image in Font applications.
www.OnBarcode.com
ECC200 Generation In None
Using Barcode printer for Font Control to generate, create Data Matrix ECC200 image in Font applications.
www.OnBarcode.com
The Init Stage
PDF 417 Generator In None
Using Barcode drawer for Font Control to generate, create PDF-417 2d barcode image in Font applications.
www.OnBarcode.com
Draw ISSN In None
Using Barcode creation for Font Control to generate, create ISSN - 13 image in Font applications.
www.OnBarcode.com
When the page request is first received by the ASP .NET engine, the Init stage ensures proper setup of the framework of the page and preparation of the controls on the page for rendering. Most controls perform their initialization at this moment. By default, the VS .NET-generated code-behind class handles the Init event of the base class to hook the InitializeComponent() method, where further component initialization may happen: Private Sub Page_Init(ByVal sender As System.Object, _ ByVal e As System.EventArgs) Handles MyBase.Init 'CODEGEN: This method call is required by the Web Form Designer 'Do not modify it using the code editor. InitializeComponent() End Sub Following this phase are a couple of smaller processes. First, if there is any viewstate, it is loaded. In other words, the ASP .NET engine looks for data that was contained in the page in a hidden <input name="_ _VIEWSTATE"> tag and has been included in the page request. If it finds any such data, it reads and decodes it, ready for use in the (re)generation of the page. In the Ch2WebForm example, this equates to collecting encoded data contained in the <input name="_ _VIEWSTATE"> tag that relates to the options in the drop-down list. Second, the postback data is processed. In the Ch2WebForm example, when the user clicks the Apply Color button, the web form fires a postback containing information for the server to process (specifically, the color selected by the user in the drop-down list).
Code39 Decoder In C#.NET
Using Barcode decoder for .NET framework Control to read, scan read, scan image in .NET applications.
www.OnBarcode.com
USS Code 39 Encoder In Java
Using Barcode creation for BIRT reports Control to generate, create Code 39 Full ASCII image in Eclipse BIRT applications.
www.OnBarcode.com
CHAPTER 2 WEB DEVELOPMENT IN .NET
Barcode Drawer In .NET Framework
Using Barcode printer for Reporting Service Control to generate, create Barcode image in Reporting Service applications.
www.OnBarcode.com
Make Code 128 In Java
Using Barcode generator for Android Control to generate, create Code 128 image in Android applications.
www.OnBarcode.com
The Load Stage
QR-Code Decoder In C#.NET
Using Barcode reader for VS .NET Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
DataMatrix Printer In C#.NET
Using Barcode creator for .NET framework Control to generate, create ECC200 image in .NET framework applications.
www.OnBarcode.com
When a page is fully initialized and any state has been properly restored (either from viewstate or postback), the main event raised is the Load event. The corresponding method you can override is OnLoad(). By default, VS .NET always adds the Page_Load() method and sets it to handle this event: Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load End Sub This is a useful facility for the developer, as this is usually the best place to add code that controls global page behavior. (In the Ch2WebForm example, you used the Page_Load() method to check whether the request was a postback, and if not, to populate the options in the dropdown list.)
Recognize Barcode In Visual C#
Using Barcode Control SDK for VS .NET Control to generate, create, read, scan barcode image in .NET framework applications.
www.OnBarcode.com
Creating GS1 - 12 In Java
Using Barcode creation for Java Control to generate, create GTIN - 12 image in Java applications.
www.OnBarcode.com
The Control Events Stage
EAN / UCC - 13 Encoder In Java
Using Barcode encoder for Java Control to generate, create USS-128 image in Java applications.
www.OnBarcode.com
Create UPC-A Supplement 5 In .NET
Using Barcode creation for Visual Studio .NET Control to generate, create UPC-A image in .NET framework applications.
www.OnBarcode.com
In the Control Events stage, the ASP .NET engine deals with a series of events that are raised and handled. If the page is being posted back, this includes events raised by the user. For example, the Click event of the btnApplyColor Button control would be handled here.
Drawing QR Code In Java
Using Barcode encoder for Java Control to generate, create QR image in Java applications.
www.OnBarcode.com
Drawing Linear In Visual C#.NET
Using Barcode maker for .NET Control to generate, create 1D Barcode image in .NET applications.
www.OnBarcode.com
Copyright © OnBarcode.com . All rights reserved.