如果前台是用字符串ajax提交，则一般是如下的写法：

                                $.ajax({
                                    url:'/Account/Authenticate',
                                    type: "post",
                                    data: JSON.stringify({"kid":cid,"UserName":encrypted_u, "PassWord":encrypted_p }),
                                    dataType: "json",
                                    contentType: "application/json;charset=UTF-8",//指定消息请求类型
                                    headers: { "RequestVerificationToken": $('@Html.AntiForgeryToken()').val() },
                                    async: false,
                                    success: function (data) {
                                        if(data.Result=="OK")
                                        {                                
                                            if(getCookie("token")!=null){delCookie("token");}
                                            location.href="/user/"; 
                                        }
                                        else
                                        {
                                            alert(data.Msg);
                                        }
                                    }
                                });

        [HttpPost]
        [ValidateAntiForgeryToken]
        [AllowAnonymous]
        public IActionResult Authenticate(string kid, string UserName, string PassWord)
        {
        ...
        }

如果前台是用AJAX提交JSON参数，一般如下写法：

                                $.ajax({
                                  type: 'POST',
                                  url:'/Account/Authenticate',
                                  data:JSON.stringify({"kid":cid,"UserName":u, "PassWord":p  }),
                                  //data: {"kid":cid,"UserName":encrypted_u, "PassWord":encrypted_p },
                                  error: function(e) {
                                    console.log(e);
                                  },
                                  dataType: "json",
                                  //    async: false,
                                  contentType: "application/json",
                                  headers: { "RequestVerificationToken": $('@Html.AntiForgeryToken()').val() },
                                  success: function (data) {
                                    if(data.Result=="OK")
                                    {                                
                                        if(getCookie("token")!=null){delCookie("token");}
                                        location.href="/admin/"; 
                                    }
                                    else
                                    {
                                        alert(data.Msg);
                                    }
                                  }
                                });

后台用以下代码接收。。。，注意NewTonJSON某个版本可能会存在解析漏洞

        [HttpPost]
        [ValidateAntiForgeryToken]
        [AllowAnonymous]
        public IActionResult Authenticate([FromBody] object json)
        {
            dynamic model = Newtonsoft.Json.Linq.JToken.Parse(json.ToString()) as dynamic;//解析
            string kid = model.kid;
            string UserName = model.UserName;
            string PassWord=model.PassWord;
            JsonResult js = Json(new { Result = "OK", Msg =  kid });
            return js;
        }