Understanding the Impact of the ?? (Null-Coalescing Operator) on C# Performance

Explore whether the null-coalescing operator in C# causes unnecessary reads and writes when updating values. Gain insights into the efficiency of conditional operations compared to the `??` operator. --- This video is based on the question https://stackoverflow.com/q/77623165/ asked by the user 'Aravaslac' ( https://stackoverflow.com/u/22036434/ ) and on the answer https://stackoverflow.com/a/77623399/ provided by the user 'D Stanley' ( https://stackoverflow.com/u/1081897/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions. Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Does using ?? (null-coalescing operator) to conditionally update a value execute unecessary read and write? Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l... The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license. If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com. --- The Efficiency of the ?? (Null-Coalescing Operator) in C# In the world of programming, every detail counts, especially when it comes to performance. When you're working with C# , one question that frequently arises is whether using the null-coalescing operator (??) results in unnecessary read and write operations. This guide delves into this topic, answering the fundamental question raised by many developers: Does using ?? execute unnecessary reads and writes when updating values? The Core Question The crux of the inquiry lies in code snippets like this: [[See Video to Reveal this Text or Code Snippet]] In this example, if qux.Foo is null, the operator falls back to bar.Foo. Is this operation optimized to avoid reading and writing if the value remains unchanged, or does it involve redundant operations? By understanding this, we can make more informed, efficient coding decisions. Typical Coding Approach The traditional method of updating the value would look like this: [[See Video to Reveal this Text or Code Snippet]] This approach ensures that bar.Foo is only updated when qux.Foo is indeed not null. It seems straightforward, but could the null-coalescing operator simplify the code while serving the same purpose? The Real Mechanics of the ?? Operator Yes, It Performs a Write Indeed, utilizing the ?? operator in the aforementioned manner does result in a write operation—every time this line of code executes, even if qux.Foo is null. This behavior stems from the fact that assigning a value to a property typically involves a setter method, which is triggered regardless of whether the value is indeed different from what is currently stored. Object References vs. Value Copies It’s essential to clarify a common misconception regarding performance impacts. When using the ?? operator, you are generally just copying a reference to an object rather than the object itself. Here's what this means: Reference Types: In C# , when working with reference types (like classes), only the reference (or pointer) is copied, which is efficient and does not significantly impact performance. Value Types: The situation changes slightly when dealing with structs (value types) that copy the entire object. However, even in these cases, using the traditional method remains just as effective. The Bottom Line: Performance Considerations In summary, while the null-coalescing operator can make your code more concise and readable, it does result in an unnecessary write operation that can potentially cause performance issues, especially if the value being assigned is large—like in the case of base64 strings. That said, for most applications, this may not lead to performance concerns if managed properly. Recommendation For optimum performance, particularly with larger objects, consider the following coding style: [[See Video to Reveal this Text or Code Snippet]] This explicit check avoids any unnecessary code execution and upholds clarity in your codebase. Conclusion Ultimately, while the ?? operator can make your code aesthetically pleasing, it's essential to weigh its usefulness against the performance implications. Always measure the impact of your coding choices, particularly in performance-critical applications. Your decision should align with both the functionality and efficiency of your codebase. Choosing the right approach can save you time and processing power, ensuring your applications run smoothly. Happy coding!