public class MyClass
{
    //Custom type Event declaration
    public event EventHandler<Mas4TEventArgs> Info;
    decimal _weigh;
    //properties
    public string Id { get; set; }
    public decimal Weigh
    {
        get { return this._weigh; }
        set                         //When this property is changed, invoke Info Event, passing Id property to be shown on messagebox.
        {
            this._weigh= value;
            Info?.Invoke(this, new Mas4TEventArgs(this.Id));
        }
    }
}