C#中ref引用传参怎么用

protected void Page_Load(object sender, EventArgs e)
        {
            int value = 0;//初始值
            Test(ref value);

            Response.Write(value.ToString());//值被改变，结果是9999
            Response.End();

        }
        protected void Test(ref int value)
        {
            value = 999;
        }