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c#.netlinqienumerableenumeration

Why is LINQ ToList not used here?

I see the following code:

using(var iterator = source.GetEnumerator()) {...}

Where source is a IEnumerable<T>.

What is the advantage of doing the above versus converting source into a List<T> and then iterating over it?

Solution

  • Converting it to a list will iterate the enumerable once and copy all the references (or even values for value types) into a new List<>. Then, you would iterate over the list. That means you would iterate twice.

    Using the IEnumerable<> as a source for enumeration iterates over the sequence only once.

    Why someone decided to do the iteration manually using the enumerator instead of leaving the details to a foreach is unclear from the small scope you posted.