Basic Information for ASP.NET Developers

1. Selecting the Correct HTTP Method

Each HTTP method is designed for a specific purpose. Choosing the right method enhances the API's usability and clarity.

• GET: Used to retrieve data.
• POST: Used to create or update a resource on the server.
• PUT: Used to fully update a resource on the server.
• PATCH: Used to partially update a resource.
• DELETE: Used to delete a resource from the server.

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2. Using Proper HTTP Response Status Codes

Every API response should be returned with the appropriate HTTP status code that indicates the result.

• 200 OK: Used for successful GET, PUT, PATCH, or DELETE requests.
• 201 Created: Used for successful POST requests.
• 204 No Content: Used for successful DELETE requests that return no content.
• 400 Bad Request: Used for requests with incorrect format or parameters.
• 401 Unauthorized: Used for requests that require authentication.
• 404 Not Found: Used when the requested resource cannot be found.
• 500 Internal Server Error: Used for server errors.

3. Designing Endpoint URLs

Endpoint URLs should be user-friendly and descriptive, providing clear information about the API's purpose and usage.

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4. Avoid Redundant Properties in Requests

In API design, unnecessary repetition should be avoided. Having the same properties multiple times creates data pollution and increases API complexity.

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5. Keeping Startup.cs Clean

In ASP.NET Core applications, the Startup.cs file contains the application's initial configuration. This file should be free from unnecessary loads and complexity, keeping only the essential configurations.

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6. Breaking Down the Project into Smaller Pieces

Dividing the project into functional units makes the code more maintainable and manageable. A modular structure increases reusability and simplifies debugging.

Incorrect Usage Example: Having all business logic, data access, and user interface code in a single project.
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• MySite.Web: web application
• MySite.API: API application
• MySite.Core: class library
• MySite.Data: class library
• MySite.Service: class library
• MySite.Logging: class library
• 
  

These three layers are commonly referred to as the Core Layer, Repository Layer, and Service Layer. Let's examine these layers in detail:

1. Core Layer: The Core layer is the innermost layer and usually includes:
• Models: Data structures used throughout the application.
• DTO (Data Transfer Object): Objects used for data transfer across layers.
• Interfaces: Interfaces used in the implementation of the Repository and Service layers, including those adhering to the Unit of Work design pattern.

The Core layer only contains definitions. Other layers perform their tasks based on the interfaces in the Core layer.

2. Repository Layer: The Repository layer manages data access operations and typically includes:
• Migration Files: Track changes to the database schema.
• Sync Files: Add initial data to the database.
• Implementations of Interfaces: Concrete implementations of interfaces from the Core layer.

The Repository layer references the Core layer and is concerned solely with data access operations.

3. Service Layer: The Service layer contains business logic and includes:
• Business Logic: Contains business rules and algorithms.
• Mapping: Manages transformations between DTO and Entity objects.
• Validation: Contains code that checks the validity of data.
• Exception Handling: Manages errors and performs other business logic-related operations.

The Service layer references both the Repository and Core layers to perform application logic.

Additional Layers: In advanced architectures, extra layers can be added, such as:

• Logging Layer: Records application processes.
• Caching Layer: Manages data caching operations.

These extra layers can be used to enhance application performance and maintain code organization.

MVC Application: This three-layer architecture can be applied to both API and MVC web applications. In API applications, only the Service layer is used, while web applications interact with the API.

7. Keeping Controller Classes and Action Methods Clean

Controller classes should only contain relevant business logic and be free from unnecessary code. Action methods should be short and adhere to the single responsibility principle.

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8. Applying Clean Code Principles

To ensure the code is readable, understandable, and easy to maintain, it's important to follow clean code principles. Adhering to coding standards, using meaningful variable and method names, and minimizing repetitive code are essential.

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9. Handling Errors Globally

The best method for managing errors throughout the application is to create a global error-handling mechanism using Middleware. This makes your application more resilient to unexpected errors.

10. Avoiding Repetitive Code

Repeating code should be refactored into separate methods or classes to make it reusable.

11. Not Returning Model Classes Directly from Action Methods

Instead of returning the data model directly from API endpoints, use DTOs (Data Transfer Objects). This is important for data security and reducing API dependencies.

12. Optimizing the Data Access Layer

The Data Access Layer (DAL) is a critical component of a .NET Core program, managing communication between the database and the application. The DAL separates business logic from data storage and provides an interface for data updating and querying.

To optimize the data access layer:

• Use asynchronous API methods to retrieve data from the database.
• Use Entity Framework Core or another suitable ORM for efficient data retrieval.
• Create well-designed SQL queries, use indexes, and minimize data retrieval.
• Enable connection pooling to efficiently manage database connections.
• Avoid using SELECT * and select only the necessary columns.
• Design data models wisely to minimize unnecessary data and joins.
• Use LINQ queries to collect and filter data.

13. Using Asynchronous Programming

Asynchronous programming in .NET Core allows tasks to run without blocking. By using the async and await keywords, you can increase efficiency, responsiveness, and performance for I/O-bound operations like network calls or database queries.

14. Utilizing Caching Techniques

Caching is an important technique that can help improve application responsiveness and performance. In .NET Core, caching types include:

• In-Memory Caching: Stores data in the application's memory.
• Distributed Caching: Shares cached data across multiple application instances.
• Response Caching: Caches HTTP responses at the server or proxy level.

15. Using Content Delivery Network (CDN)

A CDN is a geographically distributed network of servers that store and deliver web content to users from the nearest server. Using a CDN optimizes content delivery, reduces latency, and enhances the performance of web applications.

16. Enabling Compression

By reducing the size of responses, you can take advantage of ASP.NET Core's response compression features. The most commonly used compression algorithms are GZip and Deflate. Response compression reduces network traffic, improves page load times, and optimizes bandwidth usage.

How It Works:

1. Compression Algorithms:
• GZip: One of the most commonly used compression algorithms, offering high compression ratios for text-based files (HTML, CSS, JS).
• Deflate: Similar to GZip, but older and slightly less efficient.
2. Communication Between Client and Server:
• The client (usually a browser) sends an "Accept-Encoding" header with every request to the server, indicating the supported compression algorithms (e.g., Accept-Encoding: gzip, deflate).
• The server checks this header and compresses the response if it supports a compatible algorithm.
• The client receives the compressed response, decompresses it, and accesses the original content.
3. Enabling Response Compression in ASP.NET Core:
• You can enable response compression in your ASP.NET Core application using the Microsoft.AspNetCore.ResponseCompression package.
• Add response compression in the Startup.cs file.
4. Advantages of Response Compression:
• Faster Load Times: Responses are smaller in size, allowing them to be delivered more quickly to the client.
• Reduced Bandwidth Usage: Compression is particularly beneficial for mobile devices or low-bandwidth connections.
• More Efficient Use of Server Resources: Smaller responses reduce the amount of data transferred between the server and client.

Considerations:

• Not all content types benefit from compression. For example, already compressed files (e.g., .jpg, .png) will not see significant size reductions when compressed.
• Response compression can increase CPU usage, so performance should be monitored when using this feature.

17. Using Dependency Injection

Dependency injection is a technique that supports testability, maintainability, and loose coupling. .NET Core provides built-in dependency injection support.

18. Preventing Boilerplate Code

By using AutoMapper, you can automate the mapping between view models and domain models. This makes your code cleaner and more readable.

19. Ensuring Security with JWT

Use JWT (JSON Web Tokens) for secure authentication and authorization in .NET Core. This is an important step in developing a secure application.

20. Using Environment-Based Settings

Use the development environment while developing your application and the production environment when deploying it. Configuration files should be used to manage settings in different environments.

21. Bundling and Minification

Optimize the performance of web applications by reducing the size and number of CSS and JavaScript files. Bundling and minification reduce the number of HTTP requests and lead to faster download times.

Conclusion: When coding, ensure that new features do not disrupt the existing structure by activating or deactivating them with minimal changes. This is possible with clean coding and allows the application to easily adapt to its development.