[Reading Notes] event

 an event is a method that allows sending signals to indicate the occurrence of an important event. 

Using system; using system. collections. generic; using system. LINQ; using system. text; namespace event {class program {static void main (string [] ARGs) {longtask it = new longtask (); it. onpolicyprogress + = new longtask. notifyprogressdelegate (it_onnotifyprogress); it. performtask (); console. readline ();} static void it_onpolicyprogress (progressargs Pa) {console. writeline ("Progress on long task complete. {0} % complete. ", Pa. percentcomplete) ;}} class longtask {Public Delegate void policyprogressdelegate (progressargs Pa); // declare a delegate public event policyprogressdelegate onpolicyprogress; // create an event public void limit mtask () {for (INT I = 0; I <10000; I ++) {// perform some processing //... // configure y subscribers that progress was made if (I % 100 = 0) {onnotifyprogress (New progressargs (INT) I/100 ));}}}} class progressargs {public int percentcomplete; Public progressargs (INT pctcomplete) {percentcomplete = pctcomplete ;}}}

Event Overview

Events have the following features:

• The publisher determines when an event is triggered, and the user determines the operation to be performed to respond to the event.

• An event can have multiple subscribers. One subscriber can process multiple events from multiple publishers.

• Events without subscribers will never be called.

• Events are usually usedNotificationUser operations (for example, click a button in the graphic user interface or select an operation from the menu ).

• If an event has multiple subscribers, when this event is triggered, multiple events are synchronously called for processing.Program. To call events asynchronously, see call synchronous methods in asynchronous mode.

• You can use the event synchronization thread.

• In the. NET Framework class library, events are based on the eventhandler delegate and eventargs base class.