Which list/collection type is best to use in a WCF data contract?
When defining a WCF data contract, which type should one use for collections/lists?
- Should it be ICollection<T>, IList<T>, T[] or...?
- Should I use interface types or the concrete types?
- What trade offs are there to consider?
Answer
note: I'm answering this from the client's perspective - i.e. the /collectionType:<type> switch on svcutil.exe (also available in the IDE).
Personally, I tend to keep it simple and use List<T>. If you are going to do lots of data binding, BindingList<T> might be an option, but for object properties it is usually overkill. Arrays make life very hard... avoid them ;-p
Note that with .NET 3.5 the features available to each collection type blur, thanks to the extension methods on Enumerable.
Normally, Collection<T> is useful when you think you might want to subclass the collection to use the virtual extension points. This isn't really an option with WCF.
As already stated, using IList<T> etc isn't an option unless you are using assembly sharing, since the generated class won't be able to create the collection.