ASP.NET Login control, login with e-mail but e-mail is not the username (how to)?

Question

Using ASP.NET forms authentication, how would you accept an e-mail address and password, use the e-mail address to lookup the username, then log them in with the looked up username and password?

We have this card system which has employee numbers, but no one can remember their numbers. The obvious would be use the e-mail addresses for the login, but the rest of the application depends on the username being the employee number.

Thanks. Code links / examples would be great.

Our current C# solution ends with a null reference exception on:

Response.Write(Membership.GetUser().UserName);

yet both of these work fine:

string userName = Membership.GetUserNameByEmail(emailAddress);
bool successfulLogin = Membership.ValidateUser(userName, password);

Answer 1

Don't use the log in control. Just put your own text boxes there and perform your own authentication logic. If the user passes, call FormsAuthentication.RedirectFromLoginPage.

This will log them in without requiring them to enter their user name, as long as you can look it from their email.

See docs.

Answer 2

Don't change the existing login control, just override the 'Authenticate' event to do your new custom logic. Also the FormsAuthentication.SetAuthCookie() function should help you override the username issues.

I haven't compiled this, but you should get the idea:

private void OnAuthenticate(object sender, AuthenticateEventArgs e)
{
    bool successfulLogin = false;
    string userName = Membership.GetUserNameByEmail(Login1.UserName); //the email address
    successfulLogin = Membership.ValidateUser(userName, Login1.Password);

    if(successfulLogin)
      FormsAuthentication.SetAuthCookie(userName, true);

    e.Authenticated = successfulLogin;
}

Answer 3

I'm having the exact same problem. On subsequent page loads this works fine:

Response.Write(HttpContext.Current.User.Identity.Name);

But this tells me that the current user is null:

Response.Write(Membership.GetUser().UserName);