Generate temporary URL to reset password

Probably the easiest way is going to be to modify your users table to add 2 extra columns, OR if you don’t want to modify the existing table you could add a new dependent table called “UserPasswordReset” or something like that. The columns are like this:

PasswordResetToken UNIQUEIDENTIFIER,
PasswordResetExpiration DATETIME

If you go with the additional table route, you could do also add the UserID column, make it a primary key and a foriegn key reference back to your users table. A UNIQUE constraint would also be recommended. Then you simply use a Guid in your asp.net application as the token.

The flow could be something like this:

1. User requests password reset for their account
2. You insert a new record in the table (or update their user record) by setting the PasswordResetExpiration to a date in the future (DateTime.Now.AddDays(1)), and set the token to Guid.NewGuid()
3. Email the user a link to your ResetPassword.aspx page with the guid in the query string (http://www.yoursite.com/ResetPassword.aspx?token=Guid-here)
4. Use the ResetPassword.aspx page to validate the token and expiration fields. (I.E. Make sure DateTime.Now < PasswordResetExpiration)
5. Provide a simple form that allows the user to reset this password.

I know you wanted to avoid modifying the database, but it really is probably the simplest method.