yieldreturn

yieldreturn is a keyword used in C# programming that enables a method to act as an iterator. When a method contains a yield return statement, it becomes an iterator method and can return a sequence of values over time without having to construct the entire sequence in memory at once.

Instead of returning a collection all at once, an iterator method returns an IEnumerable or IEnumerator object. The compiler transforms the iterator method into a state machine. Each time the iterator method is called, execution resumes from where it left off after the last yield return statement. The yield return statement then provides the next value in the sequence to the caller.

This approach is particularly useful for handling large datasets or infinite sequences, as it allows for lazy evaluation. Only the elements needed by the caller are generated, which can significantly improve performance and reduce memory consumption.

A yield break statement can also be used within an iterator method to indicate the end of the sequence. When a yield break is encountered, the iteration terminates. Iterator methods are often used with foreach loops, making it convenient to process the generated sequence. The compiler handles the complexity of managing the state between iterations, simplifying the developer's task.