Hi Guys,

I think retrieving the service everytime shouldn't be a bottleneck or something.
However, i'd go for a member variable which i'd set when first accessed...

Use a service for when there is only one instance of that type of component. A bit like the singleton approach in a way.
I like to retrieve my services in any Loadcontent methods I may have in my classes and keep the member variable alive until the class is no longer needed.

It also depends on the nature of the service. If the service is dynamic, like a plug-in that could be pulled out at any time, then you shouldn't cache a reference.

conkerjo:

I like to retrieve my services in any Loadcontent methods I may have in my classes and keep the member variable alive until the class is no longer needed.

Ditto.

Though to be fair, knowing that you can only have one service of a certain class, I used reflector, and in the GameServiceContainer class you can see that GetService() takes it's data from a dictionary, so performance-wise it's not really that much of a hit, even if you call GetService every time.

Time to advocate for Dependency Injection and Inversion of Control and the related (yes, this is a shameless plug) Bnoerj.Sinject.

Same here.

Either use XNA's component concept and query your services in Initialize() (or LoadContent() or when needed if you wish, just not in the constructor),

or use dependency injection and add the required services as parameters to your component's constructor, any optional services as properties. Personally, I'm using Ninject with some tricks to make it work even before the Game class' constructor runs.

Most Inversion of Control containers provide their own implementation of the IServiceContainer interface, so it even integrates well with normal GameComponents if said components don't use XNA's own (slightly flawed due to the reference to the Game class) GameComponent but implement IUpdateable and optionally IDrawable themselves (I have written my own Component and DrawableComponent classes as did one of our MVPs around here, would have provided a link if I could only find it).