Razor Pages vs MVC: Server-Rendered Web Apps in ASP.NET Core

@page "{id:int}"
@model EditModel
@{
    ViewData["Title"] = "Edit product";
}

<h1>Edit product</h1>

<form method="post">
    <div asp-validation-summary="ModelOnly" class="text-danger"></div>

    <label asp-for="Input.Name"></label>
    <input asp-for="Input.Name" />
    <span asp-validation-for="Input.Name" class="text-danger"></span>

    <label asp-for="Input.Price"></label>
    <input asp-for="Input.Price" />
    <span asp-validation-for="Input.Price" class="text-danger"></span>

    <label asp-for="Input.SalePrice"></label>
    <input asp-for="Input.SalePrice" />
    <span asp-validation-for="Input.SalePrice" class="text-danger"></span>

    <button type="submit">Save</button>
</form>

@section Scripts {
    <partial name="_ValidationScriptsPartial" />
}

using System.ComponentModel.DataAnnotations;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
using Microsoft.EntityFrameworkCore;

namespace Shop.Pages.Products;

public sealed class EditModel(ShopDbContext db) : PageModel
{
    [BindProperty]
    public ProductInput Input { get; set; } = new();

    [TempData]
    public string? StatusMessage { get; set; }

    public async Task<IActionResult> OnGetAsync(int id, CancellationToken ct)
    {
        var product = await db.Products.AsNoTracking().FirstOrDefaultAsync(p => p.Id == id, ct);
        if (product is null) return NotFound();

        Input = new ProductInput
        {
            Name = product.Name, Price = product.Price, SalePrice = product.SalePrice
        };
        return Page();
    }

    public async Task<IActionResult> OnPostAsync(int id, CancellationToken ct)
    {
        if (!ModelState.IsValid) return Page(); // redisplay with validation messages

        var product = await db.Products.FindAsync([id], ct);
        if (product is null) return NotFound();

        product.Name = Input.Name;
        product.Price = Input.Price;
        product.SalePrice = Input.SalePrice;
        await db.SaveChangesAsync(ct);

        StatusMessage = $"Saved {product.Name}.";
        return RedirectToPage("./Index"); // Post/Redirect/Get
    }
}

// Only the fields a user may edit, which prevents overposting.
public sealed class ProductInput : IValidatableObject
{
    [Required, StringLength(80)]
    public string Name { get; set; } = "";

    [Range(0.01, 100_000)]
    public decimal Price { get; set; }

    [Display(Name = "Sale price")]
    public decimal? SalePrice { get; set; }

    public IEnumerable<ValidationResult> Validate(ValidationContext context)
    {
        if (SalePrice >= Price)
        {
            yield return new ValidationResult(
                "The sale price must be lower than the price.", [nameof(SalePrice)]);
        }
    }
}