PageModel in ASP.NET Core Razor Page

In ASP.NET Core Razor Pages, a PageModel is a class that serves as the code-behind for a Razor Page, encapsulating the logic and data associated with that page. It plays a crucial role in the Razor Pages framework, promoting a clean separation of concerns by separating the page’s presentation (HTML) from its behavior (C# code).

Key Features of PageModel

Model Binding: The PageModel class facilitates model binding, which maps form data or query parameters from an HTTP request to properties of the model. This makes it easier to work with user input.

Page Lifecycle: It contains methods that correspond to the page's lifecycle, such as:

• OnGet(): Called when a GET request is made to the page.
• OnPost(): Called when a POST request is made (e.g., when a form is submitted).
• Other methods for handling HTTP methods like PUT, DELETE, etc. (e.g., OnPut(), OnDelete()).
• Data and State Management: The PageModel can hold properties that represent the state of the page, such as data fetched from a database or the results of form submissions.

Dependency Injection: It supports dependency injection, allowing you to inject services (like repositories, logging, etc.) directly into the PageModel.

Validation: You can use data annotations to validate user input directly in the PageModel.

Example of a PageModel

Here’s a simple example of a PageModel for a Razor Page that handles a form submission:

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;

public class ContactModel : PageModel
{
    [BindProperty]
    public string Name { get; set; }

    [BindProperty]
    public string Email { get; set; }

    public void OnGet()
    {
        // Logic to execute on GET request (e.g., initialize data).
    }

    public IActionResult OnPost()
    {
        if (!ModelState.IsValid)
        {
            return Page(); // Return to the same page with validation errors.
        }

        // Logic to handle form submission (e.g., save data to a database).
        
        return RedirectToPage("Success"); // Redirect to a success page.
    }
}

Conclusion

The PageModel is a fundamental component in ASP.NET Core Razor Pages, enabling developers to manage the page’s behavior and data more effectively while maintaining a clean separation from the HTML markup. This structure promotes better organization and easier maintenance of web applications.