public async Task <ActionResult> DeleteClass(int?id)
        {
            if (ModelState.IsValid)
            {
                var model = await InstitutionManager.FindClassByIdAsync(id ?? 0);

                if (model != null)
                {
                    await InstitutionManager.DeleteClassAsync(model);
                }
            }
            return(RedirectToAction("AllClass"));
        }