ASP. net4-PAGE analysis

This article is based on ASP. net3.5 core programming. The following content applies to ASP. net2.0 and later versions.

The page class provides the basic behavior for creating all objects by the. aspx file. (This includes <asp:Control/> The process of generating C # description-type objects by TAG is invisible, which is automatically completed by the compiler .) Page can implement this function because it implements the ihttphandler interface. The ihttphandler interface can be used to process HTTP requests of the corresponding type (the. aspx file here ).Program. The ihttphandler interface's key method processrequest completes the process of creating all objects from the. aspx file.

The parent class templatecontrol of page defines a set of basic functions of the page (or control. The control class at the upper layer of templatecontrol defines the properties, methods, and events shared by ASP. NET Server elements (including pages, controls, and user controls. The inamingcontainer interface implemented by templatecontrol enables page to act as the control container.

PageClass attributes

Page attributes are classified into three types: built-in objects, worker attributes, and page-specific attributes. The following sections describe:

Internal object

These attributes are the secondary objects inside the page. They are the basic elements that enable normal page execution.

Genus	Description
Application	Returns an instance of the httpapplicationstate class. It indicates the status of the current application.
Cache	An instance of the cache class is returned, which implements caching for ASP. NET applications. It supports task priority and expiration (expiration), and is more efficient and more powerful than application.
Profile	Returns an instance of the profilecommon class. It represents the user-specific data set associated with the request
Request	Returns an instance of the httpresponst class. It represents the current HTTP request.
Response	Returns an instance of the httpresponse class. It is used to send HTTP response data to the client.
Server	Returns an instance of the httpserverutility class. It provides auxiliary methods for processing Web requests.
Session	Returns an instance of the httpsessionstate class. It is used to manage user-specific data.
Trace	Returns an instance of the tracecontext class. It is used to track pages.
User	Returns an object of the iprincipal type. It indicates the user who sends the request

Worker attributes

These attributes are used to carry information and provide basic functions. These attributes are essential for page programming.

Genus	Description
Clientscript	Obtains the clientscriptmanager object, which contains the client script used by the page.
Controls	Returns the word control set on the current page.
Errorpage	Indicates the attribute of the error page. In the event of an unprocessed page exception, the browser that sends the request will be redirected to the page.
Form	Returns the htmlform object of the current page.
Header	Returns the object representing the current page header. This object implements the ipageheader interface.
Isasync	Indicates whether the current page is called by an asynchronous processing program.
Iscallback	Indicates whether the currently loaded page is the result of client script callback.
Iscrosspagepostback	Indicates whether the currently loaded page is a response to another page.
Ispostback	Indicates whether the currently loaded page is a response to the client sending back or loading for the first time.
Isvalid	Used to indicate whether the page verification is successful
Master	Returns an instance of the masterpage class. It indicates the master page that determines the appearance of the current page.
Masterpagefile	Indicates the object name attribute of the master page on the current page.
Namingcontainer	Returns null.
Page	Returns the current page object (this is in C)
Pageadapter	Returns the adapter object of the current page object.
Parent	Returns null.
Previouspage	Return the reference of the main call page in cross-page sending.
Templatesourcedirectory	Obtain the virtual path of the current page
Validators	Returns a set of all verification controls on the page.
Viewstateuserkey	A string type attribute that represents a user-specific Identifier. It is used to hash the content of the view State ). This is one of the defense lines for one-click attack attacks.

Explanation: Because the page object is in the root node of the layered structure. Therefore, the namingcontainer and parent attributes always return null. Viewstateuserkey can accept user-specific information, such as the verified session ID. This attribute can be used to encrypt viewstate and so on. In addition, viewstateuserkey must be set in page_init.

Context attributes

These attributes represent the visual and non-visual attributes of the page)

Genus	Description
Clientid	Always Returns an empty string
Clientquerystring	Obtain the query string of the requested URL.
Clienttarget	The default value is an empty string, which allows developers to specify the browser type to generate correct HTML. Setting this property will disable the browser's Automatic Detection Function
Enableviewstate	Indicates whether view status information is managed on the current page. The function is equivalent to the enableviewstate attribute in @ page.
Enableviewstatemac	Indicates whether ASP. NET needs to generate a computer-specific authentication (MAC) and append it to the view status of the page.
Enabletheming	Indicates whether a topic is supported on the current page.
ID	Always Returns an empty string
Maintainscrollpositiononpostback	Used to indicate whether to restore the client browser's scroll bar position after sending back
Smartnavigation	Indicates whether to enable intelligent navigation. Smart navigation leverages a large number of unique browser functions to enhance users' experience on pages.
Stylesheettheme	The name of the style sheet applied to the current page.
Theme	The name of the topic applied to the page. Note: If the topic is set in encoding mode, it can only be performed in the preinit event.
Title	Indicates the attributes of the page title.
Traceenabled	Turn on or off the tracking feature for the current page
Tracemodevalue	Get or set the tracing Mode
Uniqueid	Always Returns an empty string
Viewstateencryptionmode	Used to indicate whether the view status and encryption method are encrypted
Visible	Indicates whether ASP. NET displays the page. ASP. NET does not generate any HTMLCodeAnd only the text written using response. Write will be sent to the client.

Three ID-related properties of the Page Object-ID, clientid, and uniqueid total return NULL strings, because these are only used for server controls and do not make sense in the page.

PageClass Method

Methods of the page class can be divided into the following categories by function. They are summarized as follows:

Method used to present (generate tag)

Method	Description
Databind	This interface is used to bind all data-binding controls on the page to the corresponding data source. The databind method itself does not generate code, but paves the way for subsequent presentation.
Rendercontrol	Outputs the current page as HTML text. If tracking is enabled, the result will contain the tracking information.
Verifyrenderinginserverform	Controls call this method when being generated to ensure that the body of the server form contains them. This method does not return values, but an exception is thrown when an error occurs.

Note: All controls whose runat attribute is server in ASP. NET must be placed in the <form> label so that they can be correctly presented by verifyrenderinginserverform.

Controls

Method	Description
Designerinitialize	When the page is in Visual Studio designer mode, this method is used to initialize the page class instance.
Findcontrol	Use the Control ID to search for it in the named container on the page. The search will not enter the sub-control that is also named container.
Gettypehashcode	Obtains the hash code generated by the ASP. xxx_aspx page class at runtime. In the base class page, the implementation of this method only returns 0, and the actual page class returns a large number
Getvalidators	Returns the set of control validators for the specified validation group.
Hascontrols	Check whether the current page contains child Controls
Loadcontrol	Compile and load the user control in the. ascx file, and a control object is returned. If the user control supports caching, partialcachingcontrol is returned.
Loadtemplate	Compile and load the user control in the. ascx file and return an instance of the internal class implementing the itemplate interface. It encapsulates the control. This internal class is named simpletemplate
Mappath	Obtain the complete physical address mapped to an absolute or relative virtual path.
Parsecontrol	Parses the input valid string and returns the control instance corresponding to the specified text tag. If the string contains multiple controls, only the first one is valid. The runat attribute is ignored. This method returns a control-type instance and must be converted to a more specific type.
Registerrequirescontrolstate	Register the control as a persistent control.
Registerrequirespostback	Registers the specified control so that it can receive the sending and receiving notifications (even if its ID does not match any ID in the returned dataset ). This control must implement the ipostbackdatahandler Interface
Registerrequiresraiseevent	Registers a specified control so that it can process input sending events. This control must implement the ipostbackeventhandler Interface
Registerviewstatehandler	This method is used to set an internal flag to maintain the current page view status. In most cases, it is used internally. If this method is not called in the pre-rendering stage, no view status is written. Generally, this method is called only by the HTML form Server Control on the page. You do not need to call
Resolveurl	Parses a relative URL into an absolute URL Based on the templatesourcedirectory property value.
Validate	Enable all verification controls on the page to verify the information they are granted. ASP. NET 2.0 supports verification groups to logically classify the controls to be verified and do not interfere with each other.

Among these methods, it is worth noting that the loadcontrol and loadtemplate Methods return control objects in addition to the return value type, the latter returns itemplate type objects, and the internal code is the same. The other difference between the two methods is that the latter does not trigger compilation, but only parses strings and infers control information. This information is used to create and initialize a control instance.

Script-related methods

The following page class methods are used to insert HTML and script code to the client page.

Method	Description
Getcallbackeventreference	Obtains the reference of a client function. When this function is called, a callback event from the client to the server is triggered.
Getpostbackclientevent	Call getcallbackeventreference
Getpostbackclienthyperlink	Append "javascript:" to the start of the string returned by getpostbackeventreference, for example, JavaScript :__ dopostback ('ctlid ','')
Getpostbackeventreference	Returns the prototype of the client script function. When the script function is called, it will cause sending back execution. It accepts a control object and a parameter. The returned string format is __dopostback ('ctlid ','')
Isclientscriptblockregistered	Determines whether the specified client script is registered on the page. This method has been marked as obsolete
Isstartupscriptregistered	Determines whether the specified client STARTUP script is registered on the page. This method has been marked as obsolete
Registerarraydeclaration	This method is used to add the ecmascript array to the client page. It accepts an array name and a string representing the array body. For example, if you call this method using thearray and 'A', 'B' as parameters, you will get the following JavaScript code: var thearray = new array ('A ', 'B '); This method has been marked as obsolete
Registerclientscriptblock	ASP. NET pages use this method to open the HTTP <form> element of the client page and add a script code block. This method has been marked as obsolete
Registerhiddenfield	Used to automatically register implicit fields with the page. This method has been marked as obsolete
Registeronsubmitstatement	This method is used to add client script code for processing onsubmit events. The script should be a JavaScript function that calls the script code registered somewhere. This method has been marked as obsolete
Registerstartupscript	ASP. NET pages use this method to add a script code block before the HTTP <form> element of the client page is closed. This method has been marked as obsolete
Setfocus	Set the browser focus on the specified control.

Many of these methods are marked as obsolete. We should use the related methods in the clientscript of page to operate the client script. When we use the registerxxx method to register a script, the script is cached in a structure and produced to the final HTML document after page rendering.

PageClass events

Some column events are triggered during the page lifecycle. These events are generally labeled as a key stage for handling reporters.

Event	Description
Aborttransaction	If the ASP. NET page is involved in an automatic transaction, this event is triggered when the transaction is aborted.
Committransaction	If the ASP. NET page is involved in an automatic transaction, this event is triggered when the transaction is committed.
Databinding	Triggered when the page's databind method is called. This method binds all child controls on the page to their corresponding data sources.
Disposed	Triggered when the page is released from memory. This event marks the final stage of the page Lifecycle
Error	Thrown when an unhandled exception is thrown
Init	Triggered when the page is initialized. This event marks the first stage of the page lifecycle.
Initcomplete	Triggered after the page and all its child controls are fully initialized. ASP. NET 1.x does not support this event
Load	After page Initialization is complete
Loadcomplete	This operation is triggered when the page loading is complete and the server event is triggered. ASP. NET 1.x does not support this event
Preinit	Triggered at the beginning of page initialization. ASP. NET 1.x does not support this event
Preload	Triggered at the beginning of page loading. ASP. NET 1.x does not support this event
Prerender	Triggered when the page is about to be rendered
Prerendercomplete	Triggered at the beginning of the page pre-rendering phase. ASP. NET 1.x does not support this event
Savestatecomplete	This is triggered when the view status of the page is stored in persistent media. ASP. NET 1.x does not support this event
Unload	It is triggered after the page is detached from the memory but not released