ASP.NET 2.0 Membership CreateUser method

[Portman]

I've used the Membership classes in an ASP.NET 2.0 application to create an
application that interfaces with an older SQL Server 2000 database.
Everything is working except the following...

Like many websites, users can sign up by filling in a form. Because we're
interacting with other databases, I eschewed the CreateUserWizard control and
wrote my own logic programmatically, making use of the
Membership.CreateUser() method.

Currently, everything is working with the user signing up using my ASP.NET
form, and then going to a login page that uses the Login control. I want to
eliminate that middle step -- a user should automatically be logged on once
they have been created.

I realize that I could re-implement my entire signup by using the
CreateUserWizard control... but is there a way to programmatically login? I
can't find it anywhere in the docs. I'm hoping for something as simple as

Membership.CreateUser(username, password);
SomeMagicClass.Authenticate(username, password);
Response.Redirect("MyProfile.aspx");

Any pointers?