Model-View-Controller (MVC)
The Model-View-Controller (MVC) architectural pattern is a widely adopted design pattern for developing user interfaces. It separates an application into three interconnected components:
The Model
The Model represents the application's data and business logic. It is responsible for managing the data, responding to requests for information about its state (usually by notifying observers), and responding to instructions to change its state. The Model is independent of the user interface. Changes to the Model can trigger updates in the View.
Key characteristics of the Model:
- Manages application data and business rules.
- Notifies observers (Views) when its state changes.
- Independent of the UI.
The View
The View is responsible for presenting the data from the Model to the user and for receiving user input. It typically displays the data in a user-friendly format. The View should be as "dumb" as possible, meaning it should not contain significant business logic. Its primary role is presentation.
Key characteristics of the View:
- Displays data from the Model.
- Handles user input and forwards it to the Controller.
- Should contain minimal logic.
The Controller
The Controller acts as an intermediary between the Model and the View. It receives user input from the View, processes it, and updates the Model accordingly. It also selects the appropriate View to display based on the user's actions and the application's state.
Key characteristics of the Controller:
- Handles user input and events.
- Interacts with the Model to update data or retrieve information.
- Selects the appropriate View to present to the user.
How they work together:
1. A user interacts with the View (e.g., clicks a button).
2. The View sends the user's action to the Controller.
3. The Controller interprets the action and updates the Model (e.g., fetches new data, performs a calculation).
4. The Model, upon state change, may notify its observers (including the View).
5. The View requests updated data from the Model and re-renders itself to reflect the changes.
Benefits of MVC
Using the MVC pattern offers several advantages:
- Separation of Concerns: Each component has a distinct responsibility, making the codebase more organized and maintainable.
- Improved Testability: Individual components can be tested in isolation.
- Code Reusability: Models can be reused with different Views, and Controllers can be adapted for various scenarios.
- Parallel Development: Different developers can work on the Model, View, and Controller simultaneously.
MVC in .NET
.NET provides robust support for building web applications using the MVC pattern. The ASP.NET MVC framework is a popular choice for developers looking to build scalable, maintainable web applications with a clear separation of concerns.
Consider the following example of a simple MVC flow:
// Controller Action
public IActionResult GetProduct(int id)
{
var product = _productService.GetProductById(id);
if (product == null)
{
return NotFound(); // View for error
}
return View("ProductDetails", product); // Pass product data to ProductDetails View
}
// Model (simplified)
public class Product
{
public int Id { get; set; }
public string Name { get; set; }
public decimal Price { get; set; }
}
// View (ProductDetails.cshtml - Razor syntax)
@model Product
@Model.Name
Price: @Model.Price.ToString("C")
This example illustrates how a Controller fetches data from a service (representing the Model's data access) and then passes that data to a specific View for rendering.