ASP.NET 自带的用户验证 COOKIE 过期之谜

 若要在收到 ASP.NET 应用程序中每个页的每个请求时模拟
Microsoft Internet 信息服务 (IIS) 身份验证用户，必须在此应用程序的 Web.config 文件中包含
<identity> 标记，并将 impersonate 属性设置为 true

<identity impersonate="true" />
<authentication mode="Forms">
<forms name="CSDN" path="/" loginUrl="~/Login.aspx"  protection="All" timeout="7200"></forms>
</authentication>

//HttpContext.Current.User = newUser;
if (AutoLogin.Checked)
{
FormsAuthentication.SetAuthCookie(UserName.Text, true);
HttpCookie httpCookie = new HttpCookie("UserName", UserName.Text);
httpCookie.Expires = DateTime.Now.AddYears(1);
Response.Cookies.Add(httpCookie);
}