Does Foreach Cache IEnumerable?

Question

Supposing that SomeMethod has signature

public IEnumerable<T> SomeMethod<T>();

is there any difference between

foreach (T tmp in SomeMethod<T>()) { ... }

and

IEnumerable<T> result = SomeMethod<T>();

foreach (T tmp in result) { ... }

In other words, will the results of SomeMethod<T> be cached on the first statement or will it be evaluated upon each iteration?

Answer 1

Assuming you're talking about C#.

foreach translates into something like this:

var enumerable = SomeMethod<T>(); // Or whatever is passed to foreach
var enumerator = enumerable.GetEnumerator();

while (enumerator.MoveNext())
{
...
}

So, as enumerable is needed only once, there will be only one call to SomeMethod even if you put it directly into the foreach statement.