问获取用户创建的方法以在属性对话框中显示时出现问题

EN

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms;
namespace testTextbox
{
    public class myTextbox : TextBox
    {
        public string _key { get; set; }
        public string _value { get; set; }
        public void aa()
        {
// aa does not appear in the properties dialogue when the text box is on the form
        }
    }
}