Custom event accessors

Program.cs

using System;

namespace create_implement_events_callbacks
{
    public class MyArgs : EventArgs
    {
        public MyArgs(int value)
        {
            Value = value;
        }
        public int Value { get; set; }
    }
    class Program
    {
        static void Main(string[] args)
        {
            var pub = new Publisher();

            pub.OnChange += (sender, e) => Console.WriteLine($"Event raised: {e.Value}");
            pub.OnChange += (sender, e) => Console.WriteLine($"Event raised: {e.Value}");

            pub.Raise();
            Console.ReadKey();
        }
    }

    public class Publisher
    {
        private event EventHandler<MyArgs> _onChange = delegate { };
        public event EventHandler<MyArgs> OnChange
        {
            add
            {
                lock (_onChange)
                {
                    _onChange += value;
                }
            }
            remove
            {
                lock (_onChange)
                {
                    _onChange -= value;
                }
            }
        }
        public void Raise()
        {
            _onChange(this, new MyArgs(30));
        }
    }
}