Comments on Dennis Doomen.NET: Coding Guidelines for C# 3.0 and C# 4.0 now availa...

Fair enough. I agree on your distinction between I...

2010-07-06T11:13:23.295+02:00

Fair enough. I agree on your distinction between IEnumerable and IQueryable. For the rest maybe it's just a matter of scope. As far as let's say internal methods are concerned (domain classes and domain services) I like the approach "return what you create", just to remind me where execution is deferred and where it isn't. Methods exposed in service boundaries, facades, and the like are a different story, though. There I tend to return the least explicit type, which in most cases would be an interface, as your guideline (1025) suggests.

Thanks Gert. I really appreciate that. For the re...

2010-07-05T16:32:56.629+02:00

Thanks Gert. I really appreciate that.

For the record, I disagree with your approach. The fact that a method or property returns an IEnumerable simply indicates that the receiver will get some kind of collection, and that it should not make any assumptions about the actual collection class.

I would never return a IQueryable as an IEnumerable. I have seen some horrible bugs because the caller wasn't aware that its evaluation was deferred. If the caller is supposed to tweak the query somehow, I make it explicit by returning an IQueryable.

A recommendable resource! Very thought-provoking, ...

2010-07-05T10:42:29.654+02:00

A recommendable resource! Very thought-provoking, even embarrassing at times... To add one of my thoughts: I could'nt agree more with AV1076 (Evaluate the result of a LINQ expression before returning it) to avoid the pitfalls of deferred execution. However, to make clear that my method returns an evaluated list I tend to return a List in stead of IEnumerable, so a consumer of the method knows that evaluating the result is not necessary. But then there is the other useful guideline, AV1025 (Return an IEnumerable or ICollection instead of a concrete collection class). To me, methods returning IEnumerable, in contrast to Lists or Arrays, convey the message that execution is deferred (as most LINQ methods do): "I just offer an enumerator, you enumerate it whenever you want". So unconsciously I made my own guideline: use IEnumerable as return type to communicate that execution may be deferred. What do you (and others) think?