Basic concepts of Events-Beginning Visual C #,

Basic concepts of Events-Beginning Visual C #,

A trigger condition is required for an event, such as timed occurrence, Mouse clicking, and the event itself. Therefore, the simplest events-related example is as follows:

// Time trigger class TimerTrigger {private Timer myTimer; public TimerTrigger () {myTimer = new Timer (100);} public TimerTrigger (int timeInterval) {myTimer = new Timer (timeInterval);} // Add the handler public void AddEventHander (ElapsedEventHandler source) with event to the time trigger {myTimer. elapsed + = source;} public void Start () {myTimer. start ();} public void Stop () {myTimer. stop () ;}} class Program {static int counter = 0; static string displayString = "This string will appear one letter at a time. "; // The Event static void WriteChar (object source, ElapsedEventArgs e) to be added to the time trigger {Console. write (displayString [counter ++ % displayString. length]);} public static void Main () {TimerTrigger timerTrigger = new TimerTrigger (100); timerTrigger. addEventHander (new ElapsedEventHandler (WriteChar); timerTrigger. start (); Console. readLine ();}}

In the main function in the preceding example, the c # ElapsedEventHandler delegated type is directly used. How can I customize the event processing function? The details are as follows:

// Custom time processing stands for public delegate void MessageHandler (string message); class TimerTrigger {private Timer myTimer; private event MessageHandler MessageArrived; public TimerTrigger (int timeInterval) {myTimer = new Timer (timeInterval); myTimer. elapsed + = new ElapsedEventHandler (CheckForMessage);} public void AddEventHandler (MessageHandler source) {MessageArrived + = source;} public void Start () {myTimer. Start ();} public void Stop () {myTimer. stop ();} private void CheckForMessage (object source, ElapsedEventArgs e) {Console. writeLine ("Checking for new messages. "); if (MessageArrived! = Null) {MessageArrived ("hello world") ;}} class Program {static int counter = 0; static void WriteFirstMessage (string message) {Console. writeLine ("The First {0} number: {1}", message, counter ++);} static void WriteSecondMessage (string message) {Console. writeLine ("The Second {0} number: {1}", message, counter ++);} public static void Main () {TimerTrigger timerTrigger = new TimerTrigger (100 ); timerTrigger. addEventHandler (new MessageHandler (WriteFirstMessage); timerTrigger. addEventHandler (new MessageHandler (WriteSecondMessage); timerTrigger. start (); Console. readLine ();}}

In the preceding example, the function used to pass a message to an event isWriteFirstMessage(string message)The passed parameter isstringType. Consider that<Timer>.ElapsedEventHandlerThe passed parameters of the function are as follows:(object source, ElapsedEventArgs e)Two parameters, can we implement a similar form? This is acceptable, as shown below:

public class MessageArrivedEventArgs : EventArgs{    private string message;    public string Message    {        get        {            return message;        }    }    public MessageArrivedEventArgs()    {        message = "No message sent.";    }    public MessageArrivedEventArgs(string newMessage)    {        message = newMessage;    }}         public delegate void MessageHandler(TimerTrigger source,    MessageArrivedEventArgs e);public class TimerTrigger{    private Timer myTimer;    private event MessageHandler MessageArrived;    public TimerTrigger(int timeInterval)    {        myTimer = new Timer(timeInterval);        myTimer.Elapsed += new ElapsedEventHandler(CheckForMessage);    }    public void AddEventHandler(MessageHandler source)    {        MessageArrived += source;     }    public void Start()    {        myTimer.Start();    }    public void Stop()    {        myTimer.Stop();    }    private void CheckForMessage(object source, ElapsedEventArgs e)    {        Console.WriteLine("Checking for new messages.");        if (MessageArrived != null)        {            MessageArrived(this, new MessageArrivedEventArgs("hello world"));        }    }}class Program{    static int counter = 0;    static void WriteFirstMessage(TimerTrigger source, MessageArrivedEventArgs e)    {        Console.WriteLine("The First {0} number: {1}", e.Message, counter++);    }    static void WriteSecondMessage(TimerTrigger source, MessageArrivedEventArgs e)    {        Console.WriteLine("The Second {0} number: {1}", e.Message, counter++);    }    public static void Main()    {        TimerTrigger timerTrigger = new TimerTrigger(100);        timerTrigger.AddEventHandler(new MessageHandler(WriteFirstMessage));        timerTrigger.AddEventHandler(new MessageHandler(WriteSecondMessage));        timerTrigger.Start();        Console.ReadLine();    }}