Model-View-Controller (MVC) is a design pattern that organizes your application into three distinct components, each with a specific responsibility: Model: Represents the data and business logic of your application. Encapsulates data access, validation rules, and any core business operations. Types of Models: Business Model (Domain Model): Represents the real-world entities and relationships of your application domain (e.g., Product, Customer, Order). View Model: A tailored model specifically designed to provide data to a view. It might aggregate data from multiple business models or contain properties for UI-specific concerns.
View: Renders the user interface (UI) based on the data provided by the controller. Typically, views are HTML templates with embedded server-side code (Razor syntax in ASP.NET Core) that dynamically generate the content.
Controller: Acts as the intermediary between the model and the view. Receives user input (from requests), interacts with the model to perform actions or retrieve data, and then selects the appropriate view to present the results.
Execution Flow of a Request in MVC Routing: The incoming request is processed by the routing middleware, which determines the appropriate controller and action method to handle it based on the URL pattern and HTTP method. Model Binding: If the action method has parameters, the model binder extracts data from the request (query string, route values, form data, body) and attempts to convert it into the types expected by the parameters. Model Validation: The model binder validates the bound data using data annotations and any custom validation logic you’ve implemented. If validation fails, errors are added to the ModelState object. Controller Action Execution: If the model is valid, the controller action method executes its logic, which might involve: Interacting with business models to retrieve or update data. Performing calculations or other business operations. Preparing a view model to pass data to the view. View Selection: The controller selects the appropriate view to render and passes the view model to it. View Rendering: The view engine (Razor) generates the HTML output based on the view template and the data in the view model. Response: The rendered HTML is sent back to the client as the HTTP response.
Responsibilities of MVC Components Controller: Handles incoming requests and routes them to the correct action methods. Interacts with the model to fetch or modify data. Selects the appropriate view and passes necessary data to it. Handles errors and redirects.
Model (Business Model): Encapsulates the business logic and data access of the application. Represents the core entities and relationships in your domain. Defines validation rules for ensuring data integrity.
View Model: Tailored for a specific view, containing only the data required by that view. Simplifies data presentation in the view and avoids exposing unnecessary details.
View: Renders the user interface based on the data provided by the controller. Uses Razor syntax to combine HTML markup with C# code for dynamic content generation.
Benefits Separation of Concerns (SoC): The clear division of responsibilities makes code more organized, maintainable, and testable. Testability: Individual components (models, views, controllers) can be tested in isolation. Reusability: Views and models can be reused in different contexts. Parallel Development: Different team members can work on different parts of the application simultaneously. Maintainability: Changes to one component are less likely to affect others. Extensibility: New features can be added more easily due to the modular structure. Scalability: MVC architecture lends itself well to scaling as the application grows.
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