public async Task <IActionResult> SuaMatHang(int id, ThemMatHangViewModel model)
        {
            var mathang = await context.MatHang.FindAsync(id);

            mathang.TenMatHang = model.TenMatHang;
            context.MatHang.Update(mathang);
            await context.SaveChangesAsync();

            return(RedirectToAction(nameof(Index)));
        }
        public async Task <IActionResult> ThemMatHang(ThemMatHangViewModel model)
        {
            var mathang = new MatHang
            {
                TenMatHang = model.TenMatHang,
            };
            await context.MatHang.AddAsync(mathang);

            await context.SaveChangesAsync();

            return(RedirectToAction(nameof(Index)));
        }