Should I use InSingletonScope when binding MembershipProvider in NInject?

Question

I am pretty new to the NInject binding, and here is what NInject describes.

• TransientBehavior-A new instance of the type will be created each time one is requested.
• SingletonBehavior-Only a single instance of the type will be created, and the same instance will be returned for each subsequent request.
• OnePerThreadBehavior-One instance of the type will be created per thread.
• OnePerRequestBehavior-One instance of the type will be created per web request, and will be destroyed when the request ends.

If I want to bind MembershipProvider to SqlMembershipProvider, should I use SingletonBehavior since I only need one sql membership provider?

Answer 1

ASP.Net already provides a static instance of the current membership provider via the static Membership class and its static Provider property. The binding would likely be in your Application_Start method and look something like this:

Bind<MembershipProvider>()
  .ToMethod(ctx => Membership.Provider);

Again, because the Memberhip.Provider is a static, it's sort of like a singleton already, so the behavior you try to apply doesn't really matter as much.

By not specifying any behavior in the above snippet, Ninject will default to a transient behavior. In this sort of a binding, I believe that will amount to calling the lambda that returns Membership.Provider every time it needs to inject a MembershipProvider type.

I suppose there could be an argument for explicitly specifying a singleton behavior as Ninject would likely "cache" the value returned by the lambda the first time it needs to inject a MembershipProvider, in effect saving the overhead of executing the lambda. I'm not 100% sure that's how Ninject would work in this situation, but it seems reasonable that it would.

All that said, my personal preference would be to use OnePerRequestBehavior, this way I know Ninject will call my lambda once for each request. Not sure it's necessary, but I like the idea of getting the provider from Membership.Provider once each request since I suppose you can't make assumptions about how or when Membership.Provider get's set, though you could probably find out if you dig enough with Reflector.

Bind<MembershipProvider>()
  .ToMethod(ctx => Membership.Provider)
  .Using<OnePerRequestBehavior>();

Good luck. Sorry your question sat out here so long!