Question

How can I make my own event in C#?

Answer 1

Here’s an example of creating and using an event with C#

using System;  namespace Event_Example {     //First we have to define a delegate that acts as a signature for the     //function that is ultimately called when the event is triggered.     //You will notice that the second parameter is of MyEventArgs type.     //This object will contain information about the triggered event.     public delegate void MyEventHandler(object source, MyEventArgs e);      //This is a class which describes the event to the class that recieves it.     //An EventArgs class must always derive from System.EventArgs.     public class MyEventArgs : EventArgs     {         private string EventInfo;         public MyEventArgs(string Text)         {             EventInfo = Text;         }         public string GetInfo()         {             return EventInfo;         }     }      //This next class is the one which contains an event and triggers it     //once an action is performed. For example, lets trigger this event     //once a variable is incremented over a particular value. Notice the     //event uses the MyEventHandler delegate to create a signature     //for the called function.     public class MyClass     {         public event MyEventHandler OnMaximum;         private int i;         private int Maximum = 10;         public int MyValue         {             get             {                 return i;             }             set             {                 if(value <= Maximum)                 {                     i = value;                 }                 else                 {                     //To make sure we only trigger the event if a handler is present                     //we check the event to make sure it's not null.                     if(OnMaximum != null)                     {                         OnMaximum(this, new MyEventArgs('You've entered ' +                             value.ToString() +                             ', but the maximum is ' +                             Maximum.ToString()));                     }                 }             }         }     }      class Program     {         //This is the actual method that will be assigned to the event handler         //within the above class. This is where we perform an action once the         //event has been triggered.         static void MaximumReached(object source, MyEventArgs e)         {             Console.WriteLine(e.GetInfo());         }          static void Main(string[] args)         {             //Now lets test the event contained in the above class.             MyClass MyObject = new MyClass();             MyObject.OnMaximum += new MyEventHandler(MaximumReached);              for(int x = 0; x <= 15; x++)             {                 MyObject.MyValue = x;             }              Console.ReadLine();         }     } }