Our last step will be to implement the "Update"
action method on our ProductController class:
Like our previous "Create" action method we'll
take advantage of the "UpdateFrom" extension method to automatically
populate our product object from the request. Notice that rather then
populate an empty product object though, we are using a pattern where we first
retrieve the old values from the database, then apply the changes the user made
to them, and then save them in the database.
Once the edit is made, we redirect back to the Product
Listing page - and automatically set the /Products/Category/[CategoryID] to
match the saved state of the Product we were working on.