16th Chapter Filter

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Note : The ActionFilterAttribute class implements both Iactionfilter and Iresultfilter interfaces. is an abstract class that requires you to provide an implementation (derived class).

Authorizeattibute and Handleerrorattribute, however, contain useful features that can be used without having to create derived classes.

Note : If a custom base class is defined for a controller, then any filter on the basis class will affect its derived class.

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First, the use of filters

　　1. Filter : The request processing that injects additional logic into the MVC framework. is the. Net annotation attribute (Attribute), which adds additional steps to the request processing pipeline.

2. Annotation Properties : a special. NET class that is derived from System.Attribute. Can be attached to other code elements (classes, methods, properties, fields, and so on).

The goal is to embed additional information into the compiled code to read back the information at run time.

In C #, the annotation properties are appended with the atttibute end, square brackets [], which can be assigned to their properties (public) with named parameter syntax.

When using the annotation attribute, the trailing attibute is omitted: authorizeattibute->[authorize]

3. Cross-focus : Can be used for the entire application, but not the ability to rotate in a local location, or will break the focus on the separation mode (login, authorization, caching, etc.).

Filter types for the MVC framework

Filter type	Interface	Default implementation	Describe
Authorization (Certified)	Iauthorizationfilter	Authorizeattibute	Run first, before any other filter or action method
Action (Action)	Iactionfilter	ActionFilterAttribute	Run before and after the action method
Result (results)	Iresultfilter	Actionfiterattribute	Run before and after the action result is executed
Exception (Exception)	Iexceptionfiter	Handleerrorattribute	Run only if another filter, action method, or action result throws an exception

　　4. Built-in authorization filter: (Authorizeattribute)

　　　　(1) Attribute Users: String A comma-delimited list of user names that allow these users to access the action method

(2) attribute Roles: String A comma-delimited list of roles. In order to access the action method, the user must be at least one of these roles

5. Exception filter: (Handleerrorattribute)

(1) The main application of abnormal filter : 1. Log the exception, 2. Display the appropriate message to the user.

Exceptioncontext Property

Name	Type	Describe
Controller	Controllerbase	Returns the requested controller object
HttpContext	HttpContextBase	Provides access to the details of the request, as well as access to the response
Ischildaction	bool	Child action judgment
RequestContext	RequestContext	Provides access to HttpContext and routed data
Routedata	Routedata	Return the requested route data

Exceptioncontext Additional Properties

Name	Type	Describe
Actiondescriptor	Actiondescriptor	Provides details of the action method
Result	ActionResult	Results for the action method
Exception	Exception	Exception not handled
Exceptionhandled	bool	Returns true if another filter has marked this exception as handled

　　

Handleerrorattribute Property

Name	Type	Describe
Exceptiontype	Type	The type of exception handled by the filter. It also handles exception types that are inherited by a given value, but ignores all other types. Default is System.Exception, which handles all standard exceptions by default
View	String	The name of the view that the filter renders. The default is error. Default Render/view/<cuttentcontrollername>/error.html or/view/shared/error.htm
Master	String	The name of the layout used when rendering the view of this filter. Default Layout page

(2) use the built-in exception filter to increase after the 〈pages〉 node in the 〈system.web〉 node in Web. config

　　　　　　　　　　　　　 ( / pages〉 〈customerrors mode= "on" defaultredirect= "/content/rangeerrorpage.html"/〉〈 / system.web〉

　　　　　　Mode: The default is RemoteOnly, which means that during development, Handleerrorattribute will not intercept the exception, but only after deployment and when a request is made from another computer.

Deaultredirect: Specifies a content page that is used when the exception message cannot be displayed in other cases.

16th Chapter Filter