C#无法写入cookie文件

我试图通过以下代码编写一个cookie文件来存储userID和userPw，但我的代码有问题，返回给我的输出总是"cookie文件不存在"。

protected void writeCookie(object sender, EventArgs e)
{
    if (Request.Cookies["save"] == null)
    {
        HttpCookie cookie = new HttpCookie("save");
        cookie.Value = "testing" + "testing2";
        cookie.Expires = DateTime.Now.AddMinutes(5);
        Request.Cookies.Add(cookie);
    }
    else
    {
        Response.Write("cookie existed");
    }
}
protected void ReadCookies(object sender, EventArgs e)
{
    if (Request.Cookies["save"] != null)
    {
        Response.Write(Request.Cookies["save"].Value);
    }
    else
    {
        Response.Write("cookies file not exist");
    }
}

Request.Cookies.Add(cookie);

Response.Cookies.Add(cookie);