public async Task <IActionResult> PutProduct(int id, Product product)
        {
            if (id != product.Id)
            {
                return(BadRequest());
            }

            _context.Entry(product).State = EntityState.Modified;

            try
            {
                await _context.SaveChangesAsync();
            }
            catch (DbUpdateConcurrencyException)
            {
                if (!ProductExists(id))
                {
                    return(NotFound());
                }
                else
                {
                    throw;
                }
            }

            return(NoContent());
        }
        public async Task <IActionResult> PutTodoItem(long id, TodoItem todoItem)
        {
            if (id != todoItem.Id)
            {
                return(BadRequest());
            }
            if (!TryValidateModel(todoItem, nameof(todoItem)))//修改后重新验证
            {
                return(BadRequest(JsonSerializer.Serialize(ModelState.Values.Where(x => x.Errors.Count > 0).Select(x => new { key = x.GetKeyValue("Key"), x.RawValue, x.Errors.First().ErrorMessage }).ToList())));
            }
            _context.Entry(todoItem).State = EntityState.Modified;

            try
            {
                await _context.SaveChangesAsync();
            }
            catch (DbUpdateConcurrencyException)
            {
                if (!TodoItemExists(id))
                {
                    return(NotFound());
                }
                else
                {
                    throw;//new Exception("");
                }
            }

            return(NoContent());
        }