get the code for the Default Membership Provider

Is is possible to get the code for the default membership provider?
I want to use the default provider to save on development time, but there is a change in the schame I need to do. I was hoping to get the code and then change this slightly.
As an example of one of the changes, I need to alter the handling of the ApplicationID. At the moment, a User can have different logins for different Applications. I want to change this so that a User can use the same login for all Applications (i.e. has the same UserID no matter which Application he is in).
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