I try to delete the product and display the error message when the product still related to many tables in database. Here the code :

[HttpPost, ActionName("Delete")]
[ValidateAntiForgeryToken]
public async Task<IActionResult> DeleteConfirmed(int id)
{
    if (_context.Products == null)
    {
        return Problem("Entity set 'ShoeContext.Products'  is null.");
    }
    var product = await _context.Products.FindAsync(id);
    if (product != null)
    {
        _context.Products.Remove(product);
        try
        {
            await _context.SaveChangesAsync();
        }
        catch (DbUpdateException ex)
        {
            if (ex.InnerException?.InnerException is SqlException sqlEx)
            {
                TempData["ErrorMessage"] = "Cant't Delete This Product";
                return RedirectToAction("Index"); 
            }
            throw;
        }
        return RedirectToAction("Index");
    }

    return RedirectToAction(nameof(Index));
}

In Index.cshtml :

@if (TempData["ErrorMessage"] != null)
{
    <div class="alert alert-danger">
        @TempData["ErrorMessage"]
    </div>
}

But Its alway show like this img . I already use UseSession in Program.cs

 builder.Services.AddSession(options =>
 {
     options.IdleTimeout = TimeSpan.FromMinutes(30);
     options.Cookie.HttpOnly = true;// Set the session timeout as needed
     options.Cookie.IsEssential = true;
 });

Does anyone know the problem ? Did I use tempdata or try catch in the wrong way? I really appreciated any instruction. Thank You