events in c# code example
Example 1: c# events
// --------------------- HOW TO CREATE EVENTS? ----------------------- //
// 1º - Main (Start the program)
// 2º - Publisher (the one that sends the event)
// 3º - Subscriber (the one that receives the event)
// PUBLISHER:
class Publisher
{
// 1º Create a delegate
public delegate void MyEventHandler (object source, EventArgs args);
// 2º Create an event based on that delegate
public event MyEventHandler myEvents;
// 3º Raise the event. For example, create a method that does:
protected virtual void Method1()
{
if(myEvents != null)
{
myEvents(this, EventArgs.Empty); // Calling the event if it points to some other method
}
}
public void Method2()
{
Console.WriteLine("This method is called from the Main function...");
// Continuation of 3º step
Method1();
}
}
// SUBSCRIBER:
public class Subscriber
{
public void Method1(object source, EventArgs e)
{
Console.WriteLine("The work done by the subscriber after the event was raised...");
}
}
// MAIN:
class Program
{
static void Main(string[] args)
{
var myPublisher = new Publisher();
var mySubscriber = new Subscriber();
// Give the Event a pointer to the function inside the class Subscriber
myPublisher.myEvents += mySubscriber.Method1;
myPublisher.Method2();
}
}
// ----------- HOW TO PASS ARGUMENTS/DATA THROUGH EVENTS? ------------ //
// You have to create an EventArgs class, like:
public class MyNewEventArgs : EventArgs // It will inherit from the EventArgs class, and you can add on top of that, some new information
{
public string newData {get; set;}
}
// Then, you just need to change the following (in the code above):
// | 1º |
public delegate void EventHandler (object source, MyNewEventArgs args); // Substitute EventArgs for MyNewEventArgs
// | 2º |
myEvents(this, new MyNewEventArgs() { newData = "Hello World!"} ); // Create an instance of the MyNewEventArgs class and pass it as a parameter of myEvents
// | 3º |
public void Method1(object source, MyNewEventArgs e) // Update all the other methods (substitute EventArgs for MyNewEventArgs)
// Now you can use the data inside the "e" variable on the Subscribers methodsExample 2: C# events
//1. (Optionally) Make a event class to return data in. Microsoft has a EventArgs class you can derive from, but benifits are minimal besides ahereance to standards.
//2. Make a event class 2 sub scribe to or that will publish the event.
//3. In any place you wish to use the event (subscribe to the event) or subscribe to the event.
/// 1. An event argument to handle the Data received
public class YourEventReceiveEventArgs : EventArgs
{
//give out any properties you wish the subscriber to have here.
//often makeing the set private so the event can be secure is a good idea.
public byte[] YourDataAsProperties { get; private set; }
public DateTime DateTime { get; private set; } = DateTime.UtcNow;
internal DataReceiveEventArgs(byte[] Data){ this.Data = Data; }
}
//2. In the Class that will be raise (creates and orignates from) the event add a delegate EventHandler
public class YourEventPublishingClass
{
//Create a delegate of the signiture of methods you would like to subscribe the event to
//Optionally: The object is sender is optional but is a ahereance to standards.
//Optionally: Add the event class that you would like to pass data in
public delegate void YourEventHandler(object Sender, DataReceiveEventArgs e);
//create Your event using your newly created signature.
public event YourEventHandler YourEvent;
//Create a way to raise your event this could be a call to check
//something durring another in anthor thread or async watch method.
protected void RaseEvent()
{
//if(Condtions are met)
if(true)
handler?.Invoke(this, e);
}
}
//3. Subscribe to event and attach a method to rase on the event
private class YourSubscriberClass
{
//using instance of the class (or you could have a static style class in some rare cases) subscribe
//note how you instance and pass the class is up to you.
private YourEventPublishingClass YourEventPublishingClassProperty;
public YourSubscriberClass(YourEventPublishingClass EventClassIn)
{
YourEventPublishingClassProperty = EventClassIn;
YourEventPublishingClassProperty.YourEvent += YourEventRecivedMethodEvent;
}
//Make sure you your event follows the signature of your delagate
private void YourEventRecivedMethodEvent(object Sender, YourEventReceiveEventArgs e)
{
//replace this with your code
}
}Example 3: why events are usefull in c#
using System;
namespace SampleApp {
public delegate string MyDel(string str);
class EventProgram {
event MyDel MyEvent;
public EventProgram() {
this.MyEvent += new MyDel(this.WelcomeUser);
}
public string WelcomeUser(string username) {
return "Welcome " + username;
}
static void Main(string[] args) {
EventProgram obj1 = new EventProgram();
string result = obj1.MyEvent("Tutorials Point");
Console.WriteLine(result);
}
}
}Example 4: c# event
private void panel1_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)
{
}
private void panel1_MouseEnter(object sender, System.EventArgs e)
private void panel1_MouseHover(object sender, System.EventArgs e)
private void panel1_MouseLeave(object sender, System.EventArgs e)
private void panel1_MouseMove(object sender, System.Windows.Forms.MouseEventArgs e)
private void panel1_MouseWheel(object sender, System.Windows.Forms.MouseEventArgs e)
private void panel1_MouseUp(object sender, System.Windows.Forms.MouseEventArgs e)
private void panel1_Paint(object sender, System.Windows.Forms.PaintEventArgs e)
private void clearButton_Click(object sender, System.EventArgs e)
0Example 5: events in c# geeksforgeeks
using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks; namespace event_programming{ //This is Subscriber Class class Program { static void Main(string[] args) { AddTwoNumbers a = new AddTwoNumbers(); //Event gets binded with delegates a.ev_OddNumber += new AddTwoNumbers.dg_OddNumber(EventMessage); a.Add(); Console.Read(); } //Delegates calls this method when event raised. static void EventMessage() { Console.WriteLine("********Event Executed : This is Odd Number**********"); } } //This is Publisher Class class AddTwoNumbers { public delegate void dg_OddNumber(); //Declared Delegate public event dg_OddNumber ev_OddNumber; //Declared Events public void Add() { int result; result = 5 + 4; Console.WriteLine(result.ToString()); //Check if result is odd number then raise event if((result % 2 != 0) && (ev_OddNumber != null)) { ev_OddNumber(); //Raised Event } } }}