C# Linq Where(expression).FirstorDefault() vs .FirstOrDefault(expression)

Question

What is the difference between these two Linq queries:

var result = ResultLists().Where( c=> c.code == "abc").FirstOrDefault(); // vs. var result = ResultLists().FirstOrDefault( c => c.code == "abc"); 

• Are the semantics exactly the same?
• Iff sematically equal, does the predicate form of FirstOrDefault offer any theoretical or practical performance benefit over Where() plus plain FirstOrDefault()?

Answer 1

Either is fine.

They both run lazily - if the source list has a million items, but the tenth item matches then both will only iterate 10 items from the source.

Performance should be almost identical and any difference would be totally insignificant.

Answer 2

The second one. All other things being equal, the iterator in the second case can stop as soon as it finds a match, where the first one must find all that match, and then pick the first of those.