I’ve been trying to update the products and add them onto the index page. However, there is something wrong with my viewmodels. I also cannot fetch other data from other viewmodels. The upsert option cannot be done. What are the possible reasons and how can I approach the problem? The list that you see doesn’t get updated.

Model:

public class ProductVM
{
    public Product Product { get; set; }

    [ValidateNever]
    public IEnumerable<SelectListItem> CategoryList { get; set; }

    
}

View:

@using Jewelry.Models.ViewModels
@model ProductVM

<div class="card shadow border-0 my-4">
    <div class="card-header bg-secondary bg-gradient ml-0 py-3">
        <div class="row">
            <div class="col-12 text-center">
                <h2 class="text-white py-2">Ürün Oluştur</h2>
            </div>
        </div>
    </div>
    <div class="card-body p-4">
        <form method="post" class="row" enctype="multipart/form-data">
            <input asp-for="Product.Id" hidden />
            <input asp-for="Product.ImageUrl" hidden />
            <div class="row">
                <div class="col-10">
                    <div class="border p-3">
                        <div class="row pb-2">
                            @* <h2 class="text-primary">Kategori Oluştur</h2> *@
                        </div>
                        @* <div asp-validation-summary="ModelOnly"></div> *@
                        <div class="form-floating py-2 col-12">
                            <input asp-for="Product.Title" class="form-control border-0 shadow" />
                            <label asp-for="Product.Title" class="ms-2"></label>
                            <span asp-validation-for="Product.Title" class="text-danger"></span>
                        </div>
                        <div class="py-2 col-12">
                            <label asp-for="Product.Description" class="ms-2"></label>
                            <textarea asp-for="Product.Description" class="form-control border-0 shadow"></textarea>
                        </div>
                        <div class="form-floating py-2 col-12">
                            <input asp-for="Product.Characteristics" class="form-control border-0 shadow" />
                            <label asp-for="Product.Characteristics" class="ms-2"></label>
                            <span asp-validation-for="Product.Characteristics" class="text-danger"></span>
                        </div>
                        <div class="form-floating py-2 col-12">
                            <input asp-for="Product.ListPrice" class="form-control border-0 shadow" />
                            <label asp-for="Product.ListPrice" class="ms-2"></label>
                            <span asp-validation-for="Product.ListPrice" class="text-danger"></span>
                        </div>
                        <div class="form-floating py-2 col-12">
                            <select asp-for="Product.CategoryId" asp-items="@Model.CategoryList" class="form-select border-0 shadow">
                                <option disabled selected>--Kategori Seç</option>
                            </select>
                            <label asp-for="Product.CategoryId" class="ms-2"></label>
                            <span asp-validation-for="Product.CategoryId" class="text-danger"></span>
                        </div>
                        <div class="form-floating py-2 col-12">
                            <input type="file" name="file" class="form-control border-0 shadow" />
                            <label asp-for="Product.ImageUrl" class=" ms-2"></label>
                        </div>
                        <div class="row">
                            <div class="col-6 col-md-3">
                                @if (Model.Product.Id != 0)
                                {
                                    <button type="submit" class="btn btn-primary form-control">Güncelle</button>
                                }
                                else
                                {
                                    <button type="submit" class="btn btn-primary form-control">Oluştur</button>
                                }

                            </div>
                            <div class="col-6 col-md-3">
                                <a asp-controller="Product" asp-action="Index" class="btn btn-outline-primary border form-control">
                                    Listeye Geri Dön
                                </a>
                            </div>
                        </div>
                    </div>

                </div>
                <div class="col-2">
                    <img src="@Model.Product.ImageUrl" width="75%"
                         style="border-radius:5px; border:1px solid #bbb9b9" />
                </div>
            </div>
        </form>

    </div>
</div>


@section Scripts {

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

}

Controller:

public IActionResult Upsert(int? id)
{

    ProductVM productVM = new()
    {
        CategoryList = _unitOfWork.Category.GetAll().Select(u => new SelectListItem
        {
            Text = u.Name,
            Value = u.Id.ToString()
        }),

        Product = new Product()
    };

    if (id == null || id == 0)
    {
        return View(productVM);
    }
    else
    {
        productVM.Product = _unitOfWork.Product.Get(u => u.Id == id);
        return View(productVM);
    }
}



[HttpPost]
public IActionResult Upsert(ProductVM productVM, IFormFile? file)
{

    if (ModelState.IsValid)
    {
        string wwwRootPath = _webHostEnvironment.WebRootPath;
        if (file != null)
        {
            string fileName = Guid.NewGuid().ToString() + Path.GetExtension(file.FileName);
            string productPath = Path.Combine(wwwRootPath, @"imagesproduct");

            if (!string.IsNullOrEmpty(productVM.Product.ImageUrl))
            {
                var oldImagePath = Path.Combine(wwwRootPath, productVM.Product.ImageUrl.TrimStart('\'));

                if (System.IO.File.Exists(oldImagePath))
                {
                    System.IO.File.Delete(oldImagePath);
                }
            }


            using (var fileStream = new FileStream(Path.Combine(productPath, fileName), FileMode.Create))
            {
                file.CopyTo(fileStream);
            }

            productVM.Product.ImageUrl = @"imagesproduct" + fileName;
        }

        if (productVM.Product.Id == 0)
        {
            _unitOfWork.Product.Add(productVM.Product);
        }

        else
        {
            _unitOfWork.Product.Update(productVM.Product);
        }


        _unitOfWork.Save();
        TempData["success"] = "Ürün başarılı bir şekilde oluşturuldu.";
        return RedirectToAction("Index");
    }
    else
    {
        productVM.CategoryList = _unitOfWork.Category.GetAll().Select(u => new SelectListItem
        {
            Text = u.Name,
            Value = u.Id.ToString()
        });

        return View(productVM);
    }

}

I tried to change the viewmodel into the model of Product only but it turns out to be wrong because of I cannot change the controller.