5 Awesome C# Refactoring Tips: Elevating Your Code to the Next Level 🏆
Tags: csharp, refactoring, tips, programming
Published: 2024-05-08 09:11:17

In this article, we’ll delve into the realm of refactoring in C#, exploring advanced techniques to improve the quality, readability, and maintainability of your code. Refactoring is an essential skill for any developer, as it allows you to optimize existing code without changing its external behavior. By applying refactoring techniques, you can enhance the structure of your codebase, making it easier to understand, test, and extend.

## Refactoring Validation Logic: Making Code More Concise and Readable

Let’s start by refactoring the validation logic in the `CustomerService` class. The current validation code is scattered throughout the `AddCustomer` [method](https://www.bytehide.com/blog/method-usage-csharp), making it hard to maintain and test. We can extract the validation logic into a separate method to improve readability and maintainability.

```csharp
// Extracting validation logic into a separate method
public bool IsValid(string firstName, string lastName, string email, DateTime dateOfBirth)
{
    const int minimumAge = 21;

    return !string.IsNullOrEmpty(firstName) &&
           !string.IsNullOrEmpty(lastName) &&
           (email.Contains('@') || email.Contains('.')) &&
           CalculateAge(dateOfBirth, DateTime.Now) >= minimumAge;
}
```

By extracting the validation logic into a separate method, we make the `AddCustomer` method more focused and easier to follow. This refactoring also paves the way for better [unit testing](https://www.bytehide.com/blog/unit-testing-csharp), as we can now test the validation logic independently.

## Introducing Dependency Injection: Embracing Inversion of Control

In the software development world, dependency injection (DI) is a design pattern that encourages the separation of concerns and promotes the principle of Inversion of Control (IoC). By applying DI, you can inject dependencies into a class rather than creating them internally, leading to more modular, reusable, and testable code.

### Why Dependency Injection?

Dependency injection offers several benefits in software development:

-   **Decoupling**: By injecting dependencies, you reduce the tight coupling between classes, making your code more flexible and easier to maintain.
-   **Testability**: With DI, you can easily replace real dependencies with mock objects during unit testing, allowing you to isolate and test individual components.
-   **Reusability**: Injected dependencies can be reused across different parts of your application, promoting code reusability and reducing duplication.
-   **Extensibility**: DI facilitates the extension of classes by allowing you to add or replace dependencies without modifying existing code.

### Implementing Dependency Injection

In C#, you can implement dependency injection using various techniques, such as constructor injection, property injection, or method injection. Constructor injection is one of the most common and recommended approaches for achieving DI.

Here’s an example of refactoring the `CustomerService` class to use constructor injection for its dependencies:

```csharp
// Using constructor injection for dependencies
public class CustomerService
{
    private readonly CompanyRepository _companyRepository;
    private readonly CustomerRepository _customerRepository;
    private readonly CreditLimitCalculator _creditLimitCalculator;

    public CustomerService(CompanyRepository companyRepository, CustomerRepository customerRepository, CreditLimitCalculator creditLimitCalculator)
    {
        _companyRepository = companyRepository;
        _customerRepository = customerRepository;
        _creditLimitCalculator = creditLimitCalculator;
    }

    // Other methods and logic go here
}
```

In this refactored version, the `CustomerService` class’s dependencies (`CompanyRepository`, `CustomerRepository`, and `CreditLimitCalculator`) are injected via the constructor. By following this approach, you achieve loose coupling between classes and enable easier unit testing.

### Benefits of Dependency Injection

By embracing dependency injection in your C# codebase, you can reap the following benefits:

-   **Simplified Maintenance**: DI leads to cleaner and more maintainable code by promoting [single responsibility](https://www.bytehide.com/blog/single-responsibility-principle-in-csharp-solid-principles) and decoupling of dependencies.
-   **Improved Testability**: With DI, you can easily create mock implementations of dependencies for unit tests, ensuring better test coverage and quality.
-   **Enhanced Flexibility**: By injecting dependencies, you allow for easy swapping of implementations, enabling flexibility and adaptability in your application.

In summary, adopting dependency injection in your C# projects can enhance the overall quality and maintainability of your codebase, making it easier to manage, extend, and test. So, consider incorporating DI principles into your software design to unlock these benefits and streamline your development process.

## Refactoring Credit Limit Calculation: Simplifying Complex Business Rules

In the world of software development, handling complex business rules efficiently is essential for maintaining a clean and understandable codebase. One area where this complexity often arises is in calculating credit limits based on different criteria. Let’s explore how we can refactor the credit limit calculation logic in the `CustomerService` class to enhance readability and extensibility using switch expressions.

### Simplifying Credit Limit Calculation

The current implementation of the credit limit calculation in the `CustomerService` class involves multiple `if-else` statements based on the type of the company. This approach can lead to code duplication and decreased maintainability. Let’s refactor this logic using a switch expression for a more concise and structured solution.

```csharp
// Refactoring credit limit calculation using switch expression
public (bool HasCreditLimit, decimal? CreditLimit) CalculateCreditLimit(Customer customer, Company company)
{
    return company.Type switch
    {
        CompanyType.VeryImportantClient => (false, null),
        CompanyType.ImportantClient => (true, GetCreditLimit(customer) * 2),
        _ => (true, GetCreditLimit(customer))
    };
}
```

In the refactored method `CalculateCreditLimit`, we utilize a switch expression to determine the credit limit based on the company type. Let’s break down the improvements and benefits of this refactoring:

### Benefits of Using Switch Expression

-   **Improved Readability**: By using a switch expression, we simplify the logic flow and make it easier to understand the conditions and outcomes.
-   **Reduced Code Duplication**: Switch expressions help eliminate repetitive code blocks, reducing the chances of errors and promoting code consistency.
-   **Ease of Extension**: Adding new business rules or company types in the future becomes more straightforward with a structured switch expression.

### Real-Life Example: Credit Limit Calculation

In a real-world scenario, consider a banking application where different types of customers have varying credit limits based on their risk profile. By refactoring the credit limit calculation logic using switch expressions, you can ensure that the code remains clear, maintainable, and adaptable to future changes.

```csharp
// Example of using CalculateCreditLimit in CustomerService
var customer = new Customer { /* customer details */ };
var company = new Company { /* company details */ };

var (hasCreditLimit, creditLimit) = CalculateCreditLimit(customer, company);

if (hasCreditLimit && creditLimit.HasValue)
{
    Console.WriteLine($"Customer has a credit limit of {creditLimit}");
}
```

In the above example, we demonstrate how the refactored `CalculateCreditLimit` method can seamlessly integrate into the overall flow of the `CustomerService` class. This refactoring approach improves the clarity and maintainability of the code, making it easier to handle complex business rules in a structured manner.

By implementing switch expressions to streamline the credit limit calculation logic, you can elevate the quality and efficiency of your codebase, ensuring a more robust and scalable solution for handling intricate business rules in your application.

## Pushing Logic Down: Enhancing Domain Model Coherence

In this final step, we explore pushing logic down into the domain model to improve the clarity and structure of the code. By introducing a static factory method in the `Customer` class and moving the credit limit check into the domain model, we enhance the cohesion and encapsulation of the domain entities.

```csharp
// Pushing logic down into the domain model
public class Customer
{
    public static Customer Create(Company company, string firstName, string lastName, string email, DateTime dateOfBirth, CreditLimitCalculator creditLimitCalculator)
    {
        // Factory method implementation
    }

    public bool IsUnderCreditLimit()
    {
        return HasCreditLimit && CreditLimit < 500;
    }
}
```

By pushing logic down into the domain model, we adhere to the single responsibility principle and improve the domain model’s encapsulation and coherence. This refactoring aligns with the object-oriented design principles, promoting a more robust and maintainable codebase.

## Wrapping Up

In this article, we’ve explored five awesome C# refactoring tips to elevate your code to the next level. By applying these advanced techniques, you can improve the quality, readability, and maintainability of your codebase. Refactoring is a continuous process, and by practicing these techniques, you can become a more proficient C# developer. So dive into your codebase, apply these refactoring tips, and watch your code transform into a masterpiece of elegance and efficiency. Happy coding!