Razor Pages Architecture question

VictorioBerra commented 1 year ago

Hello, thanks for the useful library! I know this might not be the best place for questions like this but I wanted to ask about best practices with architecture when layering an app using Ardalis.Result and things like RazorPages and FluentValidation.

Take the following example from the homepage, where we have a service that updates a BlogCategory, and leverages FluentValidation and Ardalis.Result:

BlogService (from README.md)

// ... Presumably somewhere in BlogCategoryService.cs
public async Task<Result<BlogCategory>> UpdateAsync(BlogCategory blogCategory)
{
    if (Guid.Empty == blogCategory.BlogCategoryId) return Result<BlogCategory>.NotFound();

    var validator = new BlogCategoryValidator();
    var validation = await validator.ValidateAsync(blogCategory);
    if (!validation.IsValid)
    {
        return Result<BlogCategory>.Invalid(validation.AsErrors());
    }

    var itemToUpdate = (await GetByIdAsync(blogCategory.BlogCategoryId)).Value;
    if (itemToUpdate == null)
    {
        return Result<BlogCategory>.NotFound();
    }

    itemToUpdate.Update(blogCategory.Name, blogCategory.ParentId);

    return Result<BlogCategory>.Success(await _blogCategoryRepository.UpdateAsync(itemToUpdate));
}

Razor Page

Html

@page
@model MyApp.Pages.EditBlogCategoryModel

<form method="post">
    <input type="text" asp-for="BlogCategoryEditViewModel.BlogCategoryName" />
    <input type="text" asp-for="BlogCategoryEditViewModel.BlogCategoryParentId" />
    <button type="submit">Submit</button>
</form>

Code Behind

using Ardalis.Result;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;

namespace SlackBotIron.Pages
{
    public class BlogCategoryEditViewModel
    {
        public string BlogCategoryName { get; set; }

        public int BlogCategoryParentId { get; set; }
    }

    public class EditBlogCategoryModel : PageModel
    {
        private readonly BlogCategoryService blogCategoryService;

        public EditBlogCategoryModel(BlogCategoryService blogCategoryService)
        {
            this.blogCategoryService = blogCategoryService;
        }

        [BindProperty]
        public BlogCategoryEditViewModel BlogCategoryEditViewModel { get; set; }

        public IActionResult OnGet(int blogCategoryId)
        {
            var editBlogCategoryRequest = new BlogCategory
            {
                BlogCategoryId = blogCategoryId,
                ParentId = BlogCategoryParentId,
                Name = BlogCategoryName,
            };

            var updateResult = this.blogCategoryService.UpdateAsync(editBlogCategoryRequest);

            if (updateResult.ValidationErrors.Any())
            {
                foreach (var error in updateResult.ValidationErrors)
                {
                    modelState.AddModelError(error.Identifier, error.ErrorMessage);
                }
            }

            if (updateResult.Status == ResultStatus.NotFound)
            {
                return this.NotFound();
            }
            else if (updateResult.Status == ResultStatus.Ok)
            {
                return this.RedirectToPage("/Blog/Category/Index");
            }
            else
            {
                throw new NotImplementedException($"Unexpected result status from {nameof(this.blogCategoryService)}.{nameof(this.blogCategoryService.UpdateAsync)}");
            }
        }
    }
}

My questions are:

My Razor Page needs a ViewModel, should both the ViewModel AND the Service using Ardalis use FluentValidation? That seems like I would be duplicating validation logic quite a bit. I guess the code smell here is mapping ValidationResults directly to modelState errors seems wrong. This means my UI and Service are tightly coupled right?
Or, should the Razor Page ViewModel be the same DTO accepted by this.blogCategoryService.UpdateAsync()? Or is that even more coupling?
What if I added an API that mirrored the RazorPage? This way people could update a BlogCategory both by the UI, and the API. Should I change the above architecture approach at all?

VictorioBerra commented 1 year ago

I created a project that illustrates the above, would you change anything? Mainly look at https://github.com/VictorioBerra/ArdalisResult-Architecture-Example/blob/main/ArdalisResultArch/Pages/Blog/Edit.cshtml.cs#L42

I validate the model, and I also validate in the app service (class that returns Result<>). So I validate twice.

VictorioBerra commented 1 year ago

Closing as I dont think this is the best place for this type of discussion but I would love to find a better place to talk about .NET architecture. There seems to be a lot of libraries, sample apps, Pluralsight videos and talks about Clean Code, Onion Arch, Hexigonal Arch, but very few places to actually get feedback and discuss.

ardalis / Result