How does HttpContext.Current.User.Identity.Name know which usernames exist?

Question

This is not necessarily an issue, I am just curious as to how it works. I have a method:

public static bool UserIsAuthenticated() {     bool isAuthed = false;     try     {         if (HttpContext.Current.User.Identity.Name != null)         {             if (HttpContext.Current.User.Identity.Name.Length != 0)             {                 FormsIdentity id = (FormsIdentity)HttpContext.Current.User.Identity;                 FormsAuthenticationTicket ticket = id.Ticket;                 isAuthed = true;                 string MyUserData = ticket.UserData;             }         }     }     catch { } // not authed     return isAuthed; } 

The HttpContext.Current.User.Identity.Name returns null if the user does not exist, but how does it know which usernames exist or do not exist?

Answer 1

For windows authentication

select your project.

Press F4

Disable "Anonymous Authentication" and enable "Windows Authentication"

Answer 2

The HttpContext.Current.User.Identity.Name returns null

This depends on whether the authentication mode is set to Forms or Windows in your web.config file.

For example, if I write the authentication like this:

<authentication mode="Forms"/> 

Then because the authentication mode="Forms", I will get null for the username. But if I change the authentication mode to Windows like this:

<authentication mode="Windows"/> 

I can run the application again and check for the username, and I will get the username successfully.

For more information, see System.Web.HttpContext.Current.User.Identity.Name Vs System.Environment.UserName in ASP.NET.