When the CreatedUser event is fired and the LoginCreatedUser is set to true, the new user is only logged in once the event is completed! To get the new user information use the following code…
using System.Web.Security;
...
protected void CreateUserWizard1_CreatedUser(object sender, EventArgs e)
{
TextBox serialNumberTextBox =
(TextBox)CreateUserWizardStep1.ContentTemplateContainer.FindControl("SerialNumberTextBox");
SerialNumber serial = new SerialNumber(serialNumberTextBox.Text);
serial.UserId = Membership.GetUser(CreateUserWizard1.UserName).ProviderUserKey.ToString();
serial.DateRegistered = DateTime.Now;
serial.Save();
}