LINQ and List methods

LINQ-and-List-methods.txt

Just for reference, here is a table of some old .NET 2 style List<> instance methods, and their equivalent extension methods in Linq:

METHOD IN List<>                              METHOD IN Linq
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list.Contains(item)                           query.Contains(item)

list.Exists(x => x.IsInteresting())           query.Any(x => x.IsInteresting())
list.TrueForAll(x => x.IsInteresting())       query.All(x => x.IsInteresting())

list.Find(x => x.IsInteresting())             query.FirstOrDefault(x => x.IsInteresting())
list.FindLast(x => x.IsInteresting())         query.LastOrDefault(x => x.IsInteresting())

list.FindAll(x => x.IsInteresting())          query.Where(x => x.IsInteresting())

list.ConvertAll(x => x.ProjectToSomething())  query.Select(x => x.ProjectToSomething())
Of course some of them are not entirely equivalent. In particular Linq's Where and Select use deferred execution, while FindAll and ConvertAll of List<> will execute immediately and return a reference to a new List<> instance.

FindLast will often be faster than LastOrDefault because FindLast actually searches starting from the end of the List<>. On the other hand LastOrDefault(predicate) always runs through the entire sequence (starting from the first item), and only then returns the most "recent" match.
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Note how you can use:
  myEnumerable.FirstOrDefault(predicate) vs myEnumerable.Where(predicate).FirstOrDefault()