在textbox里放按钮并控制输入字符不能覆盖住按钮(包括设计阶段)[8]

        return false

    end function

    '修改text属性时检查

    public overrides property text() as string

        get

            return mybase.text

        end get

        set(byval value as string)

            if checklength(value) then

                throw new exception("超出可以显示的范围！")