using System;

public class Program

{

    public static void Main()

    {

        var foo = new Foo();

        foo.ValueChanged += (sender, value) => Console.WriteLine($"sender: {sender}, value: {value}");

        foo.Value = 1;

        foo.Value = 2;

    }

}

​

public class Foo

{

    private int value;

    public event EventHandler<int> ValueChanged;

​

    public int Value

    {

        get

        {

            return this.value;

        }

        set

        {

            this.value = value;

            this.OnValueChanged(value);

        }

    }

​

    protected virtual void OnValueChanged(int e)

    {

        this.ValueChanged?.Invoke(this, e);

    }

}