IEnumerable as return type

by

This is really a two part question.

1) Is there inherently anything wrong with returning an IEnumerable<T>

No nothing at all. In fact if you are using C# iterators this is the expected behavior. Converting it to a List<T> or another collection class pre-emptively is not a good idea. Doing so is making an assumption on the usage pattern by your caller. I find it’s not a good idea to assume anything about the caller. They may have good reasons why they want an IEnumerable<T>. Perhaps they want to convert it to a completely different collection hierarchy (in which case a conversion to List is wasted).

2) Are there any circumstances where it may be preferable to return something other than IEnumerable<T>?

Yes. While it’s not a great idea to assume much about your callers, it’s perfectly okay to make decisions based on your own behavior. Imagine a scenario where you had a multi-threaded object which was queueing up requests into an object that was constantly being updated. In this case returning a raw IEnumerable<T> is irresponsible. As soon as the collection is modified the enumerable is invalidated and will cause an execption to occur. Instead you could take a snapshot of the structure and return that value. Say in a List<T> form. In this case I would just return the object as the direct structure (or interface).

This is certainly the rarer case though.

More Related Contents:

  1. Collection was modified; enumeration operation may not execute in ArrayList [duplicate]
  2. ReadOnlyCollection or IEnumerable for exposing member collections?
  3. How to check if IEnumerable is null or empty?
  4. Recreating a Dictionary from an IEnumerable
  5. IEnumerable and order
  6. Convert List to List
  7. The foreach identifier and closures
  8. The order of elements in Dictionary
  9. Select N random elements from a List in C#
  10. ObservableCollection that also monitors changes on the elements in collection
  11. Shorter syntax for casting from a List to a List?
  12. Count the items from a IEnumerable without iterating?
  13. Correct, idiomatic way to use custom editor templates with IEnumerable models in ASP.NET MVC
  14. How to easily initialize a list of Tuples?
  15. What .NET collection provides the fastest search
  16. Thread-safe List property
  17. How do I override List’s Add method in C#?
  18. Multi Value Dictionary?
  19. C# Sortable collection which allows duplicate keys
  20. Why do C# collection initializers work this way?
  21. Does the Enumerator of a Dictionary return key value pairs in the order they were added?
  22. Intelligent way of removing items from a List while enumerating in C#
  23. Difference between IEnumerable Count() and Length
  24. Enum to Dictionary in C#
  25. Using IEnumerable without foreach loop
  26. Case-INsensitive Dictionary with string key-type in C#
  27. how do I chunk an enumerable?
  28. Compare Two Lists Via One Property Using LINQ
  29. How add or remove object while iterating Collection in C#
  30. Why use .AsEnumerable() rather than casting to IEnumerable?

Leave a Comment