C# in Depth

364 APPENDIX LINQ standard query operatorsTable A.5Sequence equality examplesExpressionwords.SequenceEqual(new[]{"zero","one","two","three","four"})words.SequenceEqual(new[]{"ZERO","ONE","TWO","THREE","FOUR"})words.SequenceEqual(new[]{"ZERO","ONE","TWO","THREE","FOUR"},StringComparer.OrdinalIgnoreCase)ResultTrueFalseTrueA.6 GenerationOut of all the generation operators (see table A.6), only one acts on an existingsequence: DefaultIfEmpty. This returns either the original sequence if it’s not empty,or a sequence with a single element otherwise. The element is normally the defaultvalue for the sequence type, but an overload allows you to specify which value to use.There are three other generation operators that are just static methods inEnumerable:■ Range generates a sequence of integers, with the parameters specifying the firstvalue and how many values to generate.■ Repeat generates a sequence of any type by repeating a specified single valuefor a specified number of times.■ Empty generates an empty sequence of any type.All of the generation operators use deferred execution.Table A.6Generation examplesExpressionResultnumbers.DefaultIfEmpty() 0, 1, 2, 3, 4new int[0].DefaultIfEmpty()new int[0].DefaultIfEmpty(10)0 (within an IEnumerable)10 (within an IEnumerable)Enumerable.Range(15, 2) 15, 16Enumerable.Repeat(25, 2) 25, 25Enumerable.Empty()An empty IEnumerableLicensed to Rhona Hadida