this.User.Identity.IsAuthenticated 为什么总是为Fasle呢？

[禁用F3]

MVC4.5 不知为啥在其它页面 this.User.Identity.IsAuthenticated 总是fasle, this.User.Identity.Name也没有值的

//登录代码
   [HttpPost]
 public ActionResult Login(Member member)
    {
       Member loginMember = base.Context.Member.Where(a => a.Phone == member.Phone && a.Password == member.Password).FirstOrDefault();
                if (loginMember != null)
                {
 System.Web.Security.FormsAuthentication.SetAuthCookie(loginMember.Phone, true, FormsAuthentication.FormsCookiePath);
 return RedirectToAction("Home", "MyHome");
                }
}

Web.Config文件配置

 <system.web>
    <authentication mode="Forms">
      <forms domain="sdf" loginUrl="~/Mobile/Home/Login" timeout="2880"  protection="All" path="/"  ></forms>
    </authentication>
    <authorization>
      <allow  users="*"/>
    </authorization>
    <compilation debug="true" targetFramework="4.5" />
    <httpRuntime targetFramework="4.5" />
  </system.web>