Get id from current logged in user - .net core, Razor, EF core

It works very well if i remove the entire modelstate validation.

Is this a potencial solution ?
 

Dear sir.
Here is my behind code so far, the problem now is in the modelState, it is always invalide (false):

The field in the database is "(nvarchar(max), not null)", is was, i believe, created from the model.

So far so good, but when the form is submitted the modelstate is false.

How do i solve this ? The userid doesn't come from the form, it is in the server session. That works and i can see the apropriate userId in the variable.

But the modelstate is false.

File: Create.cshtml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
using Microsoft.AspNetCore.Mvc.Rendering;
using HyperWeb_V3.Data;
using HyperWeb_V3.Models;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Mvc.ModelBinding;
using Microsoft.AspNetCore.Identity.EntityFrameworkCore;
using System.Security.Claims;

namespace HyperWeb_V3.Pages.Entities
{
    [Authorize]
    public class CreateModel : PageModel
    {
        private readonly HyperWeb_V3.Data.ApplicationDbContext _context;
        private readonly UserManager _userManager; // To get current logged in user

        public CreateModel(HyperWeb_V3.Data.ApplicationDbContext context, UserManager userManager)
        {
            _context = context;
            _userManager = userManager; // To get current logged in user
        }

        public IActionResult OnGet()
        {
            return Page();
        }

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


        // To protect from overposting attacks, see https://aka.ms/RazorPagesCRUD
        public async Task OnPostAsync()
        {

            // Retrieve the currently logged in user
            var user = await _userManager.GetUserAsync(User); // To get current logged in user
            if (user == null)
            {
                return Challenge();
            }
            
            if (!ModelState.IsValid || _context.Entities == null || Entity == null)
            {
                foreach (var modelStateVal in ViewData.ModelState.Values)
                {
                    foreach (var error in modelStateVal.Errors)
                    {
                        var errorMessage = error.ErrorMessage;
                        ModelState.AddModelError("", error.ErrorMessage);
                    }
                }                
                return Page();
            }

            // Get the current user's ID and set it as the AuthorId for the Entity.
            string currentUserId = _userManager.GetUserId(User);
            Entity.AuthorId = currentUserId;

            _context.Entities.Add(Entity);
            await _context.SaveChangesAsync();

            return RedirectToPage("./Index");
        }
    }
}

Hi Rui

Here's how you can modify your code to achieve this:

1. Modify the Entity model to have an AuthorId property that will store the user's ID:

using Microsoft.AspNetCore.Identity;
using System.ComponentModel.DataAnnotations;

namespace HyperWeb_V3.Models
{
    public class Entity
    {
        [Key]
        public int Id { get; set; }

        [Required]
        [StringLength(100, MinimumLength = 3)]
        [RegularExpression(@"^[a-zA-Z0-9\s]*$",
            ErrorMessage = "Only alphanumeric characters and spaces are allowed.")]
        public string Title { get; set; }

        [Required]
        [StringLength(1000)]
        public string Description { get; set; }

        // Author ID - IMPORTANT
        public string AuthorId { get; set; } // Store the user's ID as a string.

        // Define a navigation property for the Author (optional, but can be useful).
        public IdentityUser Author { get; set; }
    }
}

In your controller action responsible for handling the form submission, you can get the current user's ID using UserManager.GetUserId(User) and set it as the AuthorId of the Entity object before saving it to the database.

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Identity;
using HyperWeb_V3.Models;
using System.Threading.Tasks;

namespace HyperWeb_V3.Controllers
{
    public class EntityController : Controller
    {
        private readonly UserManager _userManager;
        private readonly ApplicationDbContext _context;

        public EntityController(UserManager userManager, ApplicationDbContext context)
        {
            _userManager = userManager;
            _context = context;
        }

        [HttpPost]
        public async Task Create(Entity entity)
        {
            if (ModelState.IsValid)
            {
                // Get the current user's ID and set it as the AuthorId for the Entity.
                string currentUserId = _userManager.GetUserId(User);
                entity.AuthorId = currentUserId;

                // Save the entity to the database.
                _context.Entities.Add(entity);
                await _context.SaveChangesAsync();

                // Redirect to a success page or wherever you want to go after creating the entity.
                return RedirectToAction("Index", "Home");
            }

            // If the model state is not valid, redisplay the form with validation errors.
            return View(entity);
        }
    }
}

With these modifications, when a user submits the form, the Create action in the EntityController will automatically set the AuthorId property to the current user's ID and save the record to the database with the corresponding author information.