C# Code Review Checklist:
Best Practices for Efficient Code

A thorough C# code review is essential for managing software projects. Among other benefits, evaluations help improve code quality, identify performance or security issues, and make programming easier.

Yet, teams often focus too much on surface-level issues or rely mostly on automated tools.

Without systematic C# source code reviews, your team will repeatedly deal with the same preventable issues and overlook severe problems that will accumulate.

As a software development company with senior developers proficient in C-family programming languages, we understand the struggle. So, we want to show you proven review practices, address common mistakes reviewers make, and highlight some helpful tools. More importantly, we’ve prepared a comprehensive C# code review checklist to help you thoroughly check your code. 

A C# code review evaluates source code to ensure it meets established standards. For C# specifically, reviewers typically check whether the code adheres to Microsoft’s recommendations, including coding conventions, memory management, logging and debugging, dependencies, and more.

As you probably know, C# applications can be very complex and diverse—their use cases include anything from gaming engines to microservice apps. This can make it difficult and time-consuming to conduct a C# code review. However, integrating the evaluation into your development workflow will make the process much less stressful.

Unlike dynamically typed languages, where errors surface at runtime, C# enforces compile-time checks. Still, this does not eliminate the need for human oversight.

Regular evaluations are important whether you are reviewing code written in Java or C#. Systematic reviews offer several advantages across different aspects of your projects and organization:

• Early bug detection. Teams incorporate C# source code reviews early in the development to prevent deep logic flaws, deadlocks, poor resource handling, and subsequent costly rewrites.
• Consistent standards. A consistent style across the codebase reduces confusion and makes it easier to onboard new developers. 
• Enhanced team collaboration. Collective code reviews allow junior and middle developers to learn best practices. They also prevent knowledge silos, ensuring that multiple team members understand the codebase sufficiently.
• Improved code quality. High-quality C# code follows patterns that make it easier to read, update, and maintain in the long term. This means less spaghetti code or improper handling and fewer inefficient data structures.
• Stable performance. Properly optimized code performs better, which is more critical in high-load environments (like cloud services, gaming, or real-time data processing) where memory leaks must be avoided.
• Strengthened cybersecurity. Following code review guidelines for C# can prevent problems with authentication logic, cryptographic algorithms, and input validation, which may introduce security vulnerabilities. 
• Scalable architecture. Structure reviews ensure that best practices are enforced throughout the codebase, preventing excessive object creation, inefficient queries, and growth-obstructing architectural flaws.

When reviews are a high-value part of the development process, applications become faster, more reliable, and less vulnerable to hackers.

Our checklist can guide you through the key aspects of a C# code review. These guidelines will help your team evaluate both critical factors and minute details in C# code. 

Coding style and readability

Enforcing a consistent style across the codebase makes it easier to work and debug in the future. To make the codebase more reliable and easier to change, you should find and reduce “magic numbers,” repetitiveness, and scope bloat.

• Check if the organization has standard coding style guidelines and practices (as described in .editorconfig).
• Use descriptive Boolean names (for example, isValid instead of notValid) rather than negative or vague variable names.
• Make sure the code naming is uniform across the application (for example, PascalCase for classes and camelCase for fields).
• Ensure consistent formatting conventions for C# development projects (like braces placement and spacing).
• Find and replace “magic numbers” with named constants or enumerations (naming SECONDS_PER_HOUR is much easier to understand than arbitrary values).
• Look for repeated chunks of code across methods or files (to centralize them in a helper function or with enumerations).

Code organization and maintainability

Apart from readability, you should review the code’s structure and modularity. This section also checks if your team follows fundamental code-writing principles.

• Make sure larger methods (exceeding 40 lines) are split into smaller, well-named helper functions that clarify the flow.
• Check if the code follows the Single Responsibility Principle (SRP), which states that a class has only one responsibility (reason to change).
• Confirm that the team employs the Open-Closed Principle (OCP), which states that classes should be open for extension but closed for modification.
• Make sure the subtypes are modifiable for their base types without breaking functionality (Liskov Substitution Principle).
• Check whether classes are not forced to implement interfaces they don’t use (Interface Segregation Principle).
• Validate whether high-level modules use abstractions rather than concrete implementations to improve their modularity (Dependency Inversion Principle).
• See if classes are grouped by domain or functionality, avoiding broad or “catch-all” namespaces.

Warnings and errors

Focus on eliminating errors, leftover debugging artifacts, and warnings that can cause spam in production logs.

• Verify that you can run the application and pass tests on the local environment (without obscure setup steps).
• Confirm that Visual Studio or your Continuous Integration system reports zero unresolved warnings or errors.
• Check for leftover test code and debugging lines (like Console.WriteLine) before merging.
• Remove unused using statements to reduce unnecessary dependencies.

Exceptions and error handling

You should make sure the exception handling can correctly isolate failures, prevent resource leaks, and clearly inform about errors.

• Verify that try-catch-finally blocks for specific exception types (FileNotFoundException instead of a general Exception), which helps clarify logic and recovery paths.
• Make sure disposable resources are handled with using statements and closed promptly, even if exceptions happen. 
• Check if the contract in doc comments or code throws an ArgumentNullException when null is encountered to avoid null reference errors in the method.
• Scan for excessive nested try-catch blocks, possibly consolidating error handling at appropriate boundaries. 

Logging

Logging should be informative, provide meaningful insights, and not leak sensitive data. 

• Check whether exceptions are logged with sufficient context, including stack traces and user-friendly messages, to help developers pinpoint root causes.
• Ensure the organization follows proper logging frameworks (e.g., ILogger, Serilog) instead of console prints (Console.WriteLine).
• Check if the log details traces privately without leaking sensitive server configurations or internal stack traces.
• Find and remove leftover debugging breakpoints or commented debug code.
• Create tickets on issues that require extra investigation.

Advanced debugging and profiling

Examine deep analytical tools to help identify performance bottlenecks, concurrency issues, and memory leaks.

• Make sure the team uses specialized profilers (like dotTrace or PerfView) to diagnose CPU usage and memory allocation.
• Examine concurrency hotspots for lock contention, thread pool starvation, or performance-dragging race conditions.
• Check how the team addresses discovered memory leaks and other bottlenecks (do they create tickets and follow-up tasks?).
• Detect unintentional memory leaks from unreleased objects or unsubscribed events in event handlers, static collections, or background tasks.

Syncs, concurrency, and threading

Async and concurrency management keep C# applications responsive under high loads.

• Confirm that async/await is used throughout asynchronous flows.
• Check if .Result or .Wait() are used on tasks (these can freeze threads and cause deadlocks).
• Determine whether shared objects are protected by lock statements or thread-safe structures (ConcurrentDictionary) to avoid unpredictable behavior from failed synchronizations.
• Make sure the lock statements are placed in try-finally blocks when exceptions occur so the locks are released on failures.
• Confirm that the C# program doesn’t unintentionally modify collections while looping throughout it (altering in the foreach or for loop can raise an InvalidOperationException or partial data updates).

Dependency injection and configuration

This aspect of the C# code review checklist ensures that dependency injection (DI) correctly decouples components and that code configurations are easier to manage.

• Review dependency lifetimes to ensure proper usage of transient, scoped, and singleton (wrongly used lifetimes can hold data longer than intended).
• Check if the implementation for parameters and class dependencies uses abstractions for easy swapping.
• Confirm that engineers use strongly typed C# classes for configuration instead of raw key-value pairs from a configuration file (to simplify configuration structure changes and prevent runtime errors).
• Make sure the code doesn’t have hard-coded environment-specific data (like dev or production DB-URIs) to avoid re-compilation for every environment change.

Memory management and performance

The review should cover how C# apps handle loops, manage memory usage, and properly dispose of unmanaged resources.

• Inspect loops and data processing for unnecessary object allocations or LINQ queries (such as repeated ToList() calls).
• Make sure the arrays and collections are initialized with an appropriate capacity when size is known (this helps avoid repeated resizing).
• Confirm that large string concatenations use StringBuilder to reduce copying overhead (in comparison, string.Concat() or + cause high memory churn in loops).
• Check if objects contain references to null when done or adopt narrower scopes, so they don’t remain in scope longer than necessary.
• Ensure that loop boundaries match array lengths, especially in performance-critical code with manual indexing (so you don’t risk IndexOutOfRangeException).
• Verify that file I/O, network resources, and other unmanaged objects are disposed of explicitly or wrapped in using blocks.
• Make sure the generics (like List<T>, Dictionary<TKey or TValue>) and APIs with explicit types to avoid unnecessary conversions (boxing and unboxing).

Security and input validation

The C# code security review focuses on keeping the application breach-safe and ensures sensitive data doesn’t leak into logs or responses.

• Validate that sensitive credentials are not embedded in code or repositories, and instead reside in secure configuration stores and environment variables.
• Make sure that the logging system doesn’t record secrets (tokens, passwords, and other sensitive information).
• Enforce input sanitization that verifies the type, length, and format of user inputs (this helps avoid cross-site scripting and SQL injection from unvalidated user data).
• Inspect cryptographic and token usage, ensuring the systems use modern approaches (like AES 256-bit, SHA-256, and Argon2) with appropriate key sizes.
• Confirm sensitive methods and endpoints explicitly enforce authorization policies.
• Verify that invalid parameter values produce user-friendly error handling or fallback behavior (for example, unhandled exceptions may expose stack traces).

Testing and continuous integration

It’s important to check how teams handle automated tests and quality checks, specifically whether they catch all bugs and contribute to stable merges.

• Ensure test methods follow an Arrange/Act/Assert pattern (Arrange defines inputs, Act executes the functionality, and Assert verifies outcomes).
• Verify test coverage meets targets for statements, branches, and paths (for example, 80% coverage of regular commits and 90% for critical applications).
• Scrutinize test quality to ensure the tests are meaningful and cover edge cases.
• Confirm robust unit tests (NUnit, xUnit) exist for all major changes, handling typical flows, edge cases, and other exceptions.
• Check that new or modified tests in the continuous integration (CI) pipeline don’t contain duplicated code and remain consistent with existing standards.
• Research tests that randomly fail or pass without code changes and determine the cause of false negatives.
• Confirm that the tests run in isolation without being affected by prior executions.

Documentation and commenting

Documentation and comments should be detailed, properly clarifying the purpose, constraints, and usage of classes or methods. 

• Ensure that public interfaces, classes, and methods carry clear XML documentation or inline comments where needed.
• Review the correctness of the XML comments (in C#, they should be placed above methods, classes, properties, and interfaces).
• Confirm that the team documents newly introduced or updated features.
• Make sure the comments explain tricky logic or design decisions — without over-commenting on simple lines that restate code or refer to old logic.
• Make sure public APIs are sufficiently documented for clarity, as other developers may lack direct access to the implementations.
• Check the bloated comment sections for clarity and see if logic can be split into smaller methods or classes.
• Verify that the code’s expected inputs and outputs are mentioned in the documentation (if the names do not reveal the full context).

This checklist ensures consistency, but it’s not just what you evaluate that counts—it’s also how you conduct the review.

By following code review guidelines, C# projects can move even more smoothly and with fewer bugs. Let’s focus on the practices we find the most useful.

• Keep reviews small, focused, and frequent. Experience shows that a smaller scope doesn’t overwhelm developers as much and actually helps catch more defects. For instance, you can split complex logic and keep the pull request below 400 lines.
• Set up review metrics. Implement a few metrics, such as time to review, defects found per review, and review frequency, to understand how effective your code is.
• Focus on areas with higher impact. We prioritize reviewing the most problematic areas and those with the highest risk of failure, such as core business logic, security-sensitive code, and multi-threaded operations.
• Get imaginative with edge cases. The code should work correctly in all real-world scenarios, no matter how minuscule the chance of encountering them. You never know what might cause crashes and other unexpected behavior.
• Evaluate dependency risks carefully. Regularly review third-party vendors for vulnerabilities or instability (especially if they support critical operations). Clearly document manual procedures in case such as service fails.
• Mark classes correctly. Leaving classes open for unintended inheritance can lead to unpredictable code behavior. Depending on the circumstance, use sealed (when a class is not extendable), static (static and instantiated methods) and abstract (for contracts implemented by derived classes).
• Flag for loops. If reviewers see a for loop iterating without needing manual index control, suggest using foreach for better readability.
• Document and share all findings. Teams often encounter the same issues during C# code reviews. Maintain a team-wide code review guide with examples of past mistakes, best practices, and frequent pitfalls.

Now that we’ve covered the checklist and best practices, it’s time to look at the common problems reviewers may face.

It’s not uncommon for experienced developers to focus on the wrong things and overlook the red flags. Here are the common problems you should be aware of:

• Nitpicking stylistic and minor issues. You shouldn’t skip style and formatting issues, but that shouldn’t be the focus of the review. Use automated style checks (Roslyn, StyleCop) and .editorconfig to catch formatting errors, so the reviewers can focus on more pressing concerns and high-risk areas.
• Skipping architectural and concurrency checks. Include concurrency and architecture topics in your review checklist. When checking the codebase and interviewing personnel, ask about thread safety, locking, single-responsibility compliance, and dependency injection.
• Overlooking documentation. Reviewers often focus purely on code changes, ignoring whether the tests and features are updated. The evaluation should include coverage of docstrings, XML comments, README updates, and other documents.
• Ignoring test code or older lines. Do not rush past existing code or test classes. A C# source code review should look at the entire module, as new features can aggravate legacy design flaws. You should also introduce realistic boundary tests with negative inputs and conditions close to real ones.
• Giving unactionable feedback. Cryptic or one-word comments can confuse developers who may not fully grasp the nature of the problem. Provide constructive input detailing what’s incorrect and suggest possible fixes. 
• Merging pull requests too quickly. Require at least two qualified reviewers for critical components or a mandatory sign-off from a senior engineer. Additionally, consider short deployments to staging environments before merging into production.

Most of these problems can be avoided if you’re aware of them. For others, specialized tools can help.

We’ve grouped software for the .NET ecosystem that can simplify the code review process, automate style checks, and make it easier to collaborate collectively during a review.

Checklists, tips, and tools can greatly improve your review process, which will undoubtedly impact your software projects. Still, guidelines can’t replace an experienced team with senior developers.

DevCom specializes in source code review services, including numerous C# and .NET enterprise projects. Our engineers combine manual assessments with advanced static and dynamic analysis tools, working on over 50 projects quarterly. 

Do you need an immediate audit to address source code quality, architecture, and security concerns, or are you looking to make reviews a core part of your development life cycle? Drop us a line, and we’ll find a way to help.