One DbContext per web request… why?

Question

I have been reading a lot of articles explaining how to set up Entity Framework\'s DbContext so that only one is created and used per HTTP web request using var

Answer 1

One thing that's not really addressed in the question or the discussion is the fact that DbContext can't cancel changes. You can submit changes, but you can't clear out the change tree, so if you use a per request context you're out of luck if you need to throw changes away for whatever reason.

Personally I create instances of DbContext when needed - usually attached to business components that have the ability to recreate the context if required. That way I have control over the process, rather than having a single instance forced onto me. I also don't have to create the DbContext at each controller startup regardless of whether it actually gets used. Then if I still want to have per request instances I can create them in the CTOR (via DI or manually) or create them as needed in each controller method. Personally I usually take the latter approach as to avoid creating DbContext instances when they are not actually needed.

It depends from which angle you look at it too. To me the per request instance has never made sense. Does the DbContext really belong into the Http Request? In terms of behavior that's the wrong place. Your business components should be creating your context, not the Http request. Then you can create or throw away your business components as needed and never worry about the lifetime of the context.