C # make progress every day-Events

　　

The code below:

Step 1: Define a type to accommodate all additional information that needs to be sent to the Event Notification recipient

internal class NewMailEventArgs : EventArgs{      private readonly String m_from,m_to,m_subject;            Public NewMailEventArgs(string from,string to,string subject){           m_from=from;m_to=to;m_subject=subject;          }        public string From{get{return m_from;}}      Public string To{get{return m_to;}}      Public string Subject{get{return m_subject;}}          }

Note: EventArgs is only a base type that inherits other types. Many events do not have any additional information to transmit, but in our scenario, NewMailEventArgs is constructed to transmit mail information.

internal class MailManager{    public event EventHandler<NewMailEventArgs> NewMail;}

Note: NewMail is the name of this event. The event member type is EventHandler <NewMailEventArgs>. Therefore, the method prototype must take the following form:

Void MethodName (Object sender, NewMailEventArgs e );

Step 3: Define a method to notify the event registration object

Internal class MailManager {protected virtual void OnNewMail (NewMailEventArgs e) {// for thread security reasons, copy the reference of the delegate field to a temporary field EventHandler <NewMailEventArgs> temp = Interlocked. compareExchange (ref NewMail, null, null); // if (temp! = Null) temp (this, e );}}

internal class MailManager{      public void SimulateNewMail(string from,string to,string subject){            NewMailEventArgs e = new NewMailEventArgs(from,to,subject);            OnNewMail(e);    }}

Design the listener event type. Next we use the Fax type to use the event.

Internal sealed Class Fax {public Fax (MailManager mm) {mm. newMail + = FaxMsg;} // when a new email arrives, MailManager will call this method Private Void FaxMsg (object sender, NewMailEventArgs e) {Console. writeLine ("event triggered");} // execute this method. The Fax object will log out of its attention to the NewMail event Public Void Unregister (MailManager mm) {mm. newMail-= FaxMsg ;}}

Note: the C # compiler translates the + = Operator into the following code to add the object's attention to the event:

Mm. add_NewMail (new EventHandler <NewMailEventArgs> (this. FaxMsg ));

In this way, our example is complete. When a new mail is received, all methods of attention to mail events will be triggered, that is, the FaxMsg method in the example. The example helps you understand the event.