//included at the top of the global.asax file
using System.Web.Security;
using System.Security.Principal;

// Extract the forms authentication cookie
string cookieName = FormsAuthentication.FormsCookieName;
HttpCookie authCookie = Context.Request.Cookies[cookieName];

if(null == authCookie)
{
  // There is no authentication cookie.
  return;
} 
  
FormsAuthenticationTicket authTicket = null;
try
{
  authTicket = FormsAuthentication.Decrypt(authCookie.Value);
}
catch(Exception ex)
{
  return;
}

if (null == authTicket)
{
  // Cookie failed to decrypt.
  return; 
} 
  
// When the ticket was created, the UserData property was assigned a
// pipe delimited string of role names.
string[] roles = authTicket.UserData.Split(new char[]{'|'});
  
// Create an Identity object
FormsIdentity id = new FormsIdentity( authTicket ); 

// This principal will flow throughout the request.
GenericPrincipal principal = new GenericPrincipal(id, roles);
// Attach the new principal object to the current HttpContext object
Context.User = principal;

//you cannot include at the top of the global.asax file
using System.Web.Security;
using System.Security.Principal;

// This principal will flow throughout the request - you cannot find the genericprincipal object!.
GenericPrincipal principal = new GenericPrincipal(id, roles);
// Attach the new principal object to the current HttpContext object
Context.User = principal;

//you cannot include at the top of the global.asax file
using System.Web.Security;
using System.Security.Principal;