What is the difference between First() and FirstOrDefault() in LINQ when the sequence is empty?
Correct answer D. First() throws InvalidOperationException; FirstOrDefault() returns the type's default value
Explanation
First returns the first element and throws InvalidOperationException if the sequence, or the filtered sequence when a predicate is given, is empty. FirstOrDefault returns default(T) instead: null for reference types and 0 for int. Use First when an element must exist and FirstOrDefault when absence is normal, remembering that 0 may be ambiguous for value types.
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