protected void Application_PostAuthenticateRequest(Object sender, EventArgs e)
{
    CustomPrincipal newUser = new CustomPrincipal(HttpContext.Current.User.Identity.Name);
    HttpContext.Current.User = newUser;
}

public class MyRole
{
    public string Country { get; set; }
    public List<string> Roles { get; set; }
}

public interface ICustomPrincipal : System.Security.Principal.IPrincipal
{
    string userID { get; set; }
    List<MyRole> MyRoles { get; set; }
}

public class CustomPrincipal : ICustomPrincipal
{
    public IIdentity Identity { get; private set; }
    private string userRoleCacheKey { get; set; }

    public CustomPrincipal(string username)
    {
        this.userRoleCacheKey = username;
        this.Identity = new GenericIdentity(username);
        this.userID = username;
        List<MyRole> tempMyRole = new List<MyRole>();
        if (!TryGetCachedUserRoles(username, out tempMyRole))
        {
            
      MyRole myRole = new MyRole();
      myRole.Country = GetCountry(username); // Accesso al DB
      myRole.Roles = GetUserRoles(username).ToList();  // Accesso al DB
      tempMyRole.Add(myRole);
            CacheUserRoles(username, tempMyRole);
        }

        this.MyRoles = tempMyRole;
    }
  
  private bool TryGetCachedUserRoles(string username, out List<MyRole> MyRoles)
    {
        string cacheKey = userRoleCacheKey;
        HttpContext httpContext = HttpContext.Current;
        if (httpContext != null)
        {
            MyRoles = (List<MyRole>)httpContext.Cache.Get(cacheKey) ?? new List<MyRole>();
        }
        else { MyRoles = new List<MyRole>(); }

        return MyRoles.Count() > 0;
    }

    private void CacheUserRoles(string username, List<MyRole> MyRoles)
    {
        string cacheKey = userRoleCacheKey;
        HttpContext httpContext = HttpContext.Current;
        if (httpContext != null)
        {
            httpContext.Cache.Insert(cacheKey, MyRoles, null, DateTime.UtcNow.AddMinutes(15), Cache.NoSlidingExpiration); 
        }
    }
  
  public string userID { get; set; }
    public List<MyRole> MyRoles { get; set; }
    public bool IsInRole(string role)
    {
        return Identity != null && Identity.IsAuthenticated &&
        !string.IsNullOrWhiteSpace(role) && isInRole(role);
    }

    private bool isInRole(string role)
    {
    //TODO
        return true; 
    }
}