Question

I’m designing a class with several functions returning lists of objects. I noticed that debugging becomes easier when my IEnumerable<T> is converted to a List<T> since the objects can be viewed in the Watch window. However, I’m not sure if this is best practice when it comes to IEnumerable.

Q: Which is better?

public IEnumerable<MyData> GetData()
{
    return Foo();
}

public IEnumerable<MyData> GetData()
{
    return Foo().ToList();
}

Answer 1

Good practice – don’t do work unless there are good reasons/required. So unless you have special reasons – just return IEnumerable<MyData> without calling ToList()/ToArray() on it.

Potential reasons:

• function promises to complete evaluation of potentially delayed enumeration
• you expect result to be enumerated multiple times