How to properly implement user system for sessions

Question

I've never actually implemented a registration/login system before, so I'm trying my hand at making my own in C#/ASP.NET (not using ASP.NET's built-in membership provider). What I'm a little unclear on is how to utilize Session/cookies to keep a user logged in during and between sessions.

protected void Login_User(object sender, EventArgs e)
{
    string username = usernameField.Text;
    string password = passwordField.Text;
    User user = UserRepository.FindUser(username);
    if (user != null)
    {
        if (user.Password.Equals(Hash(password)))
        {
            // How do I properly login the user and keep track of his session?
        }
        else
            Response.Write("Wrong password!");
    }
    else 
        Response.Write("User does not exist!");
}

Answer 1

its quite complicate for proper login system.

1. create class that inherit System.Security.Principal.IPrincipal
2. another class that inherrit System.Security.Principal.IIdentity
3. Assign IPrincipal derivative to System.Web.HttpConext.Current.User
4. if u dont want to use cookies then put your IPrincipal to Session.
5. if HttpContext.Current.User is lost then re-assign by get from session(in very first event eg. page_init). for my code, i use FormsAuthenticationTicket as cookie and reassign at Global.asax on event PostAuthenticateRequest

the good thing of using HttpContext.Current.User is u can mark method attribute.

[Authorize] // authorized user only
public void btn_click(...){...}

i'm not sure for normal asp.net but it work very well in asp MVC

if u want to use cookies, try System.Web.Securitiy.FormsAuthenticationTicket and FormsAuthentication

sample

public class WebUser:System.Security.Principal.IPrincipal
{
  ...
  public System.Security.Principal.IIdentity Identity{get; private set;}
  public WebUser(...)
  {
    this.Identity = new WebIdentity(...);
    HttpContext.Current.User = this;
  }
}
public class WebIdentity : System.Security.Principal.IIdentity
{
  ...
}

public void Login(...)
{
  var newUser = new WebUser(...);
}