Question

I have a click event handler in class A with some logic. And now i want to access class A event handler from class B and do some logic so that class B event hadler logic fires first followed by class A event handler.

Example:

Class A
private void calculate_Click(object sender, System.EventArgs e)
{  this.MyMethod(); }

Class B
private void calculate_Click(object sender, System.EventArgs e)
{  // My new code.. (This should trigger first)  this.MyMethod(); }

Answer 1

You may use event exposed by class A and consumed by class B like we do with Button class. Button exposes click event and in our form class we subscribe for click event being exposed by Button class.

I found this simple example for understanding here

using System;
namespace wildert
{
    public class Metronome
    {
        public event TickHandler Tick;
        public EventArgs e = null;
        public delegate void TickHandler(Metronome m, EventArgs e);
        public void Start()
        {
           // while (true) //uncomment this line if you want event to fire repeatedly
            {
                System.Threading.Thread.Sleep(3000);
                if (Tick != null)
                {
                    Tick(this, e);
                }
            }
        }
    }
        public class Listener
        {
            public void Subscribe(Metronome m)
            {
                m.Tick += new Metronome.TickHandler(HeardIt);
            }
            private void HeardIt(Metronome m, EventArgs e)
            {
                System.Console.WriteLine("HEARD IT");
            }

        }
    class Test
    {
        static void Main()
        {
            Metronome m = new Metronome();
            Listener l = new Listener();
            l.Subscribe(m);
            m.Start();
        }
    }
}