C# in Depth

168 CHAPTER 6 Implementing iterators the easy wayConsole.WriteLine ("Starting to iterate");while (true){Console.WriteLine ("Calling MoveNext()...");bool result = iterator.MoveNext();Console.WriteLine ("... MoveNext result={0}", result);if (!result){break;}Console.WriteLine ("Fetching Current...");Console.WriteLine ("... Current result={0}", iterator.Current);}Listing 6.5 certainly isn’t pretty, particularly around the iteration side of things. Inthe normal course of events we’d just use a foreach loop, but to show exactly what’shappening when, I had to break the use of the iterator out into little pieces. Thiscode broadly does what foreach does, although foreach also calls Dispose at theend, which is important for iterator blocks, as we’ll see shortly. As you can see,there’s no difference in the syntax within the method even though this time we’rereturning IEnumerable instead of IEnumerator. Here’s the output fromlisting 6.5:Starting to iterateCalling MoveNext()...Start of GetEnumerator()About to yield 0... MoveNext result=TrueFetching Current...... Current result=0Calling MoveNext()...After yieldAbout to yield 1... MoveNext result=TrueFetching Current...... Current result=1Calling MoveNext()...After yieldAbout to yield 2... MoveNext result=TrueFetching Current...... Current result=2Calling MoveNext()...After yieldYielding final value... MoveNext result=TrueFetching Current...... Current result=-1Calling MoveNext()...End of GetEnumerator()... MoveNext result=FalseThere are various important things to note from this output:Licensed to Rhona Hadida