public async Task <IActionResult> SendWeixin(string openId)
        {
            if (string.IsNullOrEmpty(openId))
            {
                return(View());
            }

            var vm = new SendWeixinViewModel();

            vm.Received = await _db.ReceivedTextMessages.Where(x => x.To == openId).ToListAsync();

            vm.OpenId = openId;
            return(View(vm));
        }
        public async Task <IActionResult> SendWeixin_Post(SendWeixinViewModel vm)
        {
            if (!ModelState.IsValid)
            {
                return(View(vm));
            }

            var token  = _weixinAccessToken.GetToken();
            var result = await Custom.SendText(token, vm.OpenId, vm.Content);

            if (!result.Succeeded)
            {
                ModelState.AddModelError("", result.errmsg);
                return(View(vm));
            }

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