Differentiate between ASP.NET Core MVC and ASP.NET Core Web API?

ASP.NET Core MVC and ASP.NET Core Web API are both frameworks for building web applications in ASP.NET Core, but they serve different purposes and have distinct characteristics. Here’s a detailed comparison, highlighting their differences and providing examples:

1. Purpose and Use Cases

ASP.NET Core MVC:

• Purpose: ASP.NET Core MVC is used for building web applications that generate dynamic HTML content. It is ideal for applications with complex user interfaces where server-side rendering of HTML is required.
• Use Cases: Websites, web applications with interactive user interfaces, forms, and views.

ASP.NET Core Web API:

• Purpose: ASP.NET Core Web API is used for building HTTP services that expose data and functionalities through HTTP endpoints. It is ideal for applications that need to provide data to clients, such as mobile apps, single-page applications (SPAs), and other web services.
• Use Cases: RESTful APIs, microservices, backend services for mobile and web applications.

2. Response Types

ASP.NET Core MVC:

• Response Type: Typically returns HTML content. It uses Razor views to render HTML responses.
• Example:

  public class HomeController : Controller
  {
      public IActionResult Index()
      {
          return View(); // Returns a Razor view (HTML)
      }
  }

ASP.NET Core Web API:

• Response Type: Typically returns JSON or XML content. It is designed to return data in formats that are consumable by clients, often using JSON.
• Example:

  [ApiController]
  [Route("api/[controller]")]
  public class ProductsController : ControllerBase
  {
      [HttpGet]
      public IActionResult Get()
      {
          var products = new List<Product>
          {
              new Product { Id = 1, Name = "Product1" },
              new Product { Id = 2, Name = "Product2" }
          };
          return Ok(products); // Returns JSON
      }
  }

3. Routing

ASP.NET Core MVC:

• Routing: Uses conventional routing or attribute routing to map URLs to controllers and actions. Routes typically include placeholders for action names, controller names, and route parameters.
• Example:

  // Conventional Routing in Startup.cs
  app.UseEndpoints(endpoints =>
  {
      endpoints.MapControllerRoute(
          name: "default",
          pattern: "{controller=Home}/{action=Index}/{id?}");
  });
   
  // Attribute Routing in Controller
  [Route("home/[action]")]
  public class HomeController : Controller
  {
      public IActionResult Index() { ... }
  }

ASP.NET Core Web API:

• Routing: Uses attribute routing to define routes directly on action methods. Routes are often more granular and specific, typically including HTTP methods.
• Example:

  [ApiController]
  [Route("api/[controller]")]
  public class ProductsController : ControllerBase
  {
      [HttpGet("{id}")]
      public IActionResult Get(int id)
      {
          // Retrieves a product by ID
      }
  }

4. Model Binding and Validation

ASP.NET Core MVC:

• Model Binding: Binds form data, query strings, route data, and posted files to action method parameters or model properties.
• Validation: Supports server-side validation using data annotations and custom validation attributes.
• Example:

  public class Product
  {
      [Required]
      public string Name { get; set; }
  }
   
  [HttpPost]
  public IActionResult Create(Product product)
  {
      if (ModelState.IsValid)
      {
          // Save product
      }
      return View(product); // Return to a Razor view
  }

ASP.NET Core Web API:

• Model Binding: Binds JSON or XML payloads from HTTP requests to action method parameters or model properties.
• Validation: Supports server-side validation using data annotations and model validation in API requests.
• Example:

  [HttpPost]
  public IActionResult Create([FromBody] Product product)
  {
      if (!ModelState.IsValid)
      {
          return BadRequest(ModelState); // Return validation errors
      }
      // Save product
      return CreatedAtAction(nameof(Get), new { id = product.Id }, product);
  }

5. Error Handling and Responses

ASP.NET Core MVC:

• Error Handling: Uses view-based error pages for user-friendly error messages. Errors are typically displayed in Razor views.
• Example:

  public IActionResult Error()
  {
      // Return an error view
      return View();
  }

ASP.NET Core Web API:

• Error Handling: Uses standardized HTTP status codes and error responses, often with a JSON payload describing the error.
• Example:

  [HttpGet("{id}")]
  public IActionResult Get(int id)
  {
      var product = _repository.GetById(id);
      if (product == null)
      {
          return NotFound(); // Returns 404 Not Found
      }
      return Ok(product); // Returns 200 OK with JSON
  }

6. Dependency Injection

Both ASP.NET Core MVC and ASP.NET Core Web API use dependency injection to manage services, but they apply it differently based on their respective purposes.

ASP.NET Core MVC:

• Example:

  public void ConfigureServices(IServiceCollection services)
  {
      services.AddControllersWithViews();
      services.AddScoped<IMyService, MyService>();
  }

ASP.NET Core Web API:

• Example:

  public void ConfigureServices(IServiceCollection services)
  {
      services.AddControllers();
      services.AddScoped<IMyService, MyService>();
  }

7. Return Types and Content Negotiation

ASP.NET Core MVC:

• Return Types: Typically returns views or redirects, and sometimes JSON if needed.
• Content Negotiation: Primarily focused on returning HTML views but can handle JSON/XML if necessary.

ASP.NET Core Web API:

• Return Types: Primarily returns JSON or XML data, with built-in support for content negotiation.
• Content Negotiation: Automatically handles the negotiation of content types based on request headers (e.g., Accept: application/json).

Conclusion

• ASP.NET Core MVC is best suited for applications that require server-side rendering of HTML and user interactions through views. It is ideal for traditional web applications with rich user interfaces.
• ASP.NET Core Web API is designed for creating RESTful services that provide data to clients and handle various types of HTTP requests and responses. It is ideal for applications that need to expose data and services via APIs, such as SPAs, mobile apps, and other client applications.

Both frameworks are part of the ASP.NET Core ecosystem, and you can use them together in a single application to leverage their respective strengths.