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C# › LINQ

What is the difference between First, FirstOrDefault and Single?

Intermediate

Answer

First returns the first match or throws if none; FirstOrDefault returns default if none; Single expects exactly one and throws otherwise.
var a = xs.First(x => x.Id==1);
var b = xs.FirstOrDefault(x => x.Id==1);
var c = xs.Single(x => x.Id==1);
Real-world example Use Single for a unique-key lookup where duplicates would indicate a data bug.
All 18 LINQ questions