MVC :: Share Session In 3 Projects?

I have created two websites ,such as [URL] and [URL]; The two websites both use SQL Sever Session Mode and they use the same database for sessionstate management.

in [URL],I have a controller as below:

public class HomeController : Controller
{
public ActionResult Index()
{
ViewBag.Message = "Welcome to A Site!";
Session["User"] = 123;
return View();
}
}

[URL] I have a controller as below:

public class HomeController : Controller
{
public ActionResult Index()
{
if (Session["User"] != null)
{
ViewBag.Message = "Welcome to B Site!" + Session["User"].ToString();
return View();
}
else
{
ViewBag.Message = "Welcome to B Site!" ;
return View();
}
}
}

if I access [URL] first ,then access [URL], I will get the response :Welcome to B Site!123 if I access [URL] first,then access [URL] then access [URL],I will get the response:Welcome to B Site.