// C# Extension Method

// Doc: https://csharp-extension.com/en/method/1002358/eventhandler-raiseevent

​

// @nuget: Z.ExtensionMethods

​

using System;

public class Program

{

    public static void Main()

    {

        Adder a = new Adder();

        a.OnMultipleOfFiveReached += a_MultipleOfFiveReached;

        int iAnswer = a.Add(4, 3);

        Console.WriteLine("iAnswer = {0}", iAnswer);

        iAnswer = a.Add(4, 6);

        Console.WriteLine("iAnswer = {0}", iAnswer);

    }

​

    static void a_MultipleOfFiveReached(object sender, EventArgs e)

    {

        Console.WriteLine("Multiple of five reached!");

    }

}

​

public class Adder

{

    public event EventHandler OnMultipleOfFiveReached;

​

    public int Add(int x, int y)

    {

        int iSum = x + y;

        if ((iSum % 5 == 0) && (OnMultipleOfFiveReached != null))

        {

            //C# Extension Method: EventHandler - RaiseEvent

            OnMultipleOfFiveReached.RaiseEvent(EventArgs.Empty);

        }

        return iSum;

    }

}

​