Page.User.Identity.Name is blank on pages of subdomains

I have multiple subdomains trying to use a single subdomain for authentiction using forms authentication all running on windows server 2008 r2.

All of the forms authentication pages are setup to use the same name, and on the authentication page the cookie is added with the following snippet:

 FormsAuthentication.SetAuthCookie(txtUserName.Text, false);
 System.Web.HttpCookie MyCookie = System.Web.Security.FormsAuthentication.GetAuthCookie(User.Identity.Name.ToString(), false);
 MyCookie.Domain = ConfigurationManager.AppSettings["domainName"];
 Response.AppendCookie(MyCookie);

When I am logged in to signon.mysite.com the page.user.identity.isauthenticated and page.user.identity.name properties both work fine. When I navigate to subdomain.mysite.com the page.user.identity.isauthenticated returns true, bue the name is empty.

I tried to retrieve it from the cookie using the following, but it also was blank.

 HttpCookie cookie = Request.Cookies[".ASPXAUTH"];
 FormsAuthenticationTicket fat = FormsAuthentication.Decrypt(cookie.Value);
 user2_lbl.Text = fat.Name;

When googling the issue I found some people saying something must be added to global.asax and other saying it wasn't necessary.

The goal is to be able to开发者_如何学C login on the authentication subdomain and have the user identity accessible from the root site and other subdomains. Machine keys match in all web.config, and the AppSettings["domainName"] is set to "mysite.com" currently.

Does anyone know what is preventing me from accessing the user information?

Change "mysite.com" to be ".mysite.com" (note the leading ".").

That'll tell the browser that the cookie is valid for subdomains as well.