ASP.NET Core MVC 2.1 Identity

I am making an application in ASP.NET Core 2.1 MVC, in which I am using Identity for user authentication, I have a class called Folder which has a relation with ApplicationUser this IdentityUser deriba, the relationship is as follows Una Folder can belong to a User and a User can have many folders when creating a folder records everything well but when I want to edit that folder the first error I have is the Edit of Get where the id = 1 but when it arrives to the Edit of the Post that same id = 0 where it does not update and redirects me to a blank page, then the other error is that when I want to edit the folder and it has a relationship with Department, Province, Municipality I recover their values but not with Users.

// GET: Carpetass/Edit/5
    public async Task<IActionResult> Edit(int? id)
    {        
        if (id == null)
        {
            return NotFound();
        }

        var carpeta = await _context.Carpetas.FindAsync(id);

        ViewData["DepartamentoId"] = new SelectList(_context.Departamentos, "DepartamentoId", "Nombre");

        var fullNames = await _context.Users.ToListAsync();// Select(u => new { UserID = u.Id, FullName = u.Nombres + " " + u.Apellidos }).ToList();

        //var fullNames = await _context.Users.ToListAsync();

        **ViewData["Id"] = new SelectList(await _context.Users.ToListAsync(), "Id", "FullName");**
        //ViewData["Id"] = _context.Users.Select(u => u.FullName).ToList();


        ViewData["ProvinciaId"] = new SelectList(_context.Provincias, "ProvinciaId", "Nombre");
        ViewData["MunicipioId"] = new SelectList(_context.Municipios, "MunicipioId", "Nombre");
        ViewData["UbicacionId"] = new SelectList(_context.Ubicaciones, "UbicacionId", "Nombre");

        //ViewData["Id"] = new SelectList(_context.Users, "Id", "FullName", resolucion.Id);
        //ViewData["UsersId"] = new SelectList(_context.Users.ToList(), "Id", "FullName", carpeta.Id);
        //ViewData["UsersId"] = new SelectList(_context.Users.ToList(), "Id", "FullName");


        if (carpeta == null)
        {
            return NotFound();
        }

        return View(carpeta);            
    }

    // POST: Carpetass/Edit/5
    // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
    // more details see http://go.microsoft.com/fwlink/?LinkId=317598.
    [HttpPost]
    [ValidateAntiForgeryToken]
    public async Task<IActionResult> Edit(int id, [Bind("CarpetaId,IDCarpeta,AgrupacionSocial,Cuerpos,Fojas,Poligono,Id,DepartamentoId,ProvinciaId,MunicipioId,UbicacionId")] Carpeta carpeta)
    {
        if (id != carpeta.CarpetaId)
        {
            return NotFound();
        }

        if (ModelState.IsValid)
        {
            try
            {
                _context.Update(carpeta);
                await _context.SaveChangesAsync();
            }
            catch (DbUpdateConcurrencyException)
            {
                if (!CarpetasExists(carpeta.CarpetaId))
                {
                    return NotFound();
                }
                else
                {
                    throw;
                }
            }
            return RedirectToAction(nameof(Index));
        }
        return View(carpeta);
    }

According to tests the problem is in this line of code in both cases.

ViewData ["Id"] = new SelectList (await _context.Users.ToListAsync (), "Id", "FullName");

First, it does not grab the user's Id and second, it changes the 0's in the post.

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