WCF and size of DTOs

Question

We've got a business logic/data access layer that we're exposing on a couple of different endpoints via a WCF service. We've created DTOs for use as the data contract of the service. We'll be using the service via the different endpoints for multiple different applications. In some of the applications, we only need a few fields from the DTO while in others we may need almost all of them. For those in which we only need a few, we really don't want to be sending the entire object "over the wire" every time - we'd like to pare it down to what we actually need for a given application.

I've gone back and forth between creating specific sets of DTOs for use with each application (overkill?) and using something like EmitDefaultValue=false on the members that are only needed in certain apps. I've also considered using the XmlSerializer rather than DataContractSerializer in order to have greater control over the serialization within the service.

My question is - first off, should we worry that much about the size of data we're passing? Second, assuming the answer is 'yes' or that we decide to care about it even if it is 'no', what approach is recommended here and why?

EDIT

Thanks for the responses so far. I was concerned we might be getting into premature optimizations. I'd like to leave the question open for now, however, in hopes that I can get some answers to the rest of it, both for my own edification and in case anybody else has this question and has a valid reason to need to optimize.

Answer 1

first off, should we worry that much about the size of data we're passing?

You didn't give the number/sizes of the fields but in general: No. You've already got the envelope(s) and the overhead of setting up the channel, a few more bytes won't matter much.

So unless we're talking about hundreds of doubles or something similar, I would first wait and if there's a real problem: experiment and measure.

Answer 2

Should you worry? Maybe. Performance/stress test your services and find out.

If you decide you do care...a couple options:

1. Create a different service (or maybe different operations in the same service) that return partially hydrated DataContracts. So these new services and/or operations return the same DataContrcts, but only partially hydrated.

2. Create "lite" versions of your DataContracts and return those instead. Basically the same as option 1, but with this approach you don't have to worry about consumers misusing the full DataContract (potentially getting null reference exceptions and such).

I prefer option 2, but if you have control over your consumers, option 1 might work for you.

Answer 3

It seems you may be entering the "premature optimization" zone. I'd avoid using application specific DataContracts for an entity because of the maintenance work it will cause problems in the long run. However, if your application has a valid need to hide information from some client applications and not other then its good to have multiple DataContracts for a given entity. @Henk is right, unless you're dealing with massive deeply nested entities (in which case you have a different problem) then do not "optimize" your design simply to reduce network transmission packets.