Microsoft Certified Solutions Developer (MCSD) Certification Practice Test

What is the yield keyword used for in C#?

1. To declare constants

2. To implement iterators

3. To manage exceptions

4. To define events

The correct answer is: To implement iterators

The yield keyword in C# is used to implement iterators, which is designed to simplify the process of creating enumerable collections. When a method, operator, or get accessor uses yield, it enables it to return each element of a collection one at a time, preserving the state of the method between calls. This allows developers to iterate through a collection without the need to create a temporary collection that holds all the elements. When using yield return, the method returns the next value in the iteration, and when the enumerator is called again, it resumes execution right after the yield return statement. This is particularly useful for creating performance-sensitive algorithms that need to return results on demand, rather than all at once. The other options do not accurately reflect the purpose of the yield keyword: constants are declared using the const keyword, exception management is handled with try-catch blocks, and events are defined using delegates and event accessors. This reaffirms the importance of recognizing the specific use cases and functionality provided by the yield keyword in the context of C#.