怎样重写已定义的时间比如onclick事件，我想传个其他参数进去，除了object和eventarg

   public delegate void onclickeventhandler（object sender,myeventargs e);

 public partial class form1 : form
    {

        public event onclickeventhandler myonclick;
    }

    public class myeventargs : eventargs
    {
        private string _para;

        public myeventargs（string para)
        {
            _para = para;
        }

        public string param
        {
            get
            {
                return _para;
            }
        }
    }

public delegate void onclickeventhandler（object sender,eventargs e,string mypara);
 public partial class form1 : form
    {

        public event onclickeventhandler myonclick;
    }