Java vs. C#

Event Handling

Java
 
//All event listeners are designed by interface.
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;

class EventDemo extends JFrame
{
   
    public EventDemo()
    {
        JButton clickMe = new JButton();

        setTitle("Event Demo");
        clickMe.setText("Click Me");
      
        //add event listener
        clickMe.addActionListener(new EventHandler());
        
        Container con = getContentPane();
        
        //use layout manager to position a button
        con.setLayout(new FlowLayout());
        con.add(clickMe);
        
        setSize(500,400);
        setVisible(true);
        setDefaultCloseOperation(DISPOSE_ON_CLOSE );
        
        JOptionPane.showMessageDialog(EventDemo.this, 
                                  "I Just Started!");
        
    }

    //inner class to deal with event listener
    class EventHandler implements ActionListener 
    {
        public void actionPerformed(ActionEvent ae) {
            JOptionPane.showMessageDialog(EventDemo.this,
                               "You Clicked My Button!");
        }
    }

    public static void main(String[] args)
    {
        new EventDemo();
    }
}

C#
 
//Events and delegates work together
using System;
using System.Drawing;
using System.Windows.Forms;

// custom delegate
public delegate void StartDelegate();

class EventDemo : Form
{
    // custom event
    public event StartDelegate StartEvent;

    public EventDemo()
    {
        Button clickMe = new Button();

        clickMe.Parent = this;
        clickMe.Text = "Click Me";
        clickMe.Location = new Point(
            (ClientSize.Width - clickMe.Width) /2,
            (ClientSize.Height - clickMe.Height)/2);

        // an EventHandler delegate is assigned
        // to the button's Click event
        clickMe.Click += new EventHandler(OnClickMeClicked);

        // our custom "StartDelegate" delegate is assigned
        // to our custom "StartEvent" event.
        StartEvent += new StartDelegate(OnStartEvent);

        // fire our custom event
        StartEvent();
    }

    // this method is called when the "clickMe" button is pressed
    public void OnClickMeClicked(object sender, EventArgs ea)
    {
        MessageBox.Show("You Clicked My Button!");
    }

    // this method is called when the "StartEvent" Event is fired
    public void OnStartEvent()
    {
        MessageBox.Show("I Just Started!");
    }

    static void Main(string[] args)
    {
        Application.Run(new EventDemo());
    }
}